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 $210.28   10.469%   $232.2942   $232.29   $232.30   $232.30  
  Purchase #2 $89.41   13.295%   $101.2971   $101.30   $101.30   $101.30  
  Purchase #3 $116.75   8.298%   $126.4379   $126.44   $126.45   $126.40  
  Purchase #4 $202.50   3.736%   $210.0654   $210.07   $210.05   $210.10  
  Purchase #5 $143.46   4.514%   $149.9358   $149.94   $149.95   $149.90  
  Purchase #6 $19.60   10.548%   $21.6674   $21.67   $21.65   $21.70  
  Purchase #7 $236.59   6.717%   $252.4818   $252.48   $252.50   $252.50  
  7 purchase totals = $1,018.59       $1,094.1796   $1,094.19   $1,094.20   $1,094.20