Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.50   10.643%   $126.6862   $126.69   $126.70   $126.70  
  Purchase #2 $218.44   5.132%   $229.6503   $229.65   $229.65   $229.70  
  Purchase #3 $103.94   11.671%   $116.0708   $116.07   $116.05   $116.10  
  Purchase #4 $211.92   10.180%   $233.4935   $233.49   $233.50   $233.50  
  Purchase #5 $202.37   11.215%   $225.0658   $225.07   $225.05   $225.10  
  Purchase #6 $244.93   11.135%   $272.203   $272.20   $272.20   $272.20  
  Purchase #7 $155.28   12.367%   $174.4835   $174.48   $174.50   $174.50  
  7 purchase totals = $1,251.38       $1,377.6531   $1,377.65   $1,377.65   $1,377.80