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 $63.49   13.644%   $72.1526   $72.15   $72.15   $72.20  
  Purchase #2 $211.28   3.442%   $218.5523   $218.55   $218.55   $218.60  
  Purchase #3 $198.79   13.671%   $225.9666   $225.97   $225.95   $226.00  
  Purchase #4 $234.91   13.222%   $265.9698   $265.97   $265.95   $266.00  
  Purchase #5 $247.80   10.292%   $273.3036   $273.30   $273.30   $273.30  
  Purchase #6 $216.62   8.174%   $234.3265   $234.33   $234.35   $234.30  
  Purchase #7 $55.57   8.375%   $60.224   $60.22   $60.20   $60.20  
  7 purchase totals = $1,228.46       $1,350.4954   $1,350.49   $1,350.45   $1,350.60