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 $41.28   7.329%   $44.3054   $44.31   $44.30   $44.30  
  Purchase #2 $245.38   6.782%   $262.0217   $262.02   $262.00   $262.00  
  Purchase #3 $141.30   7.304%   $151.6206   $151.62   $151.60   $151.60  
  Purchase #4 $125.57   8.188%   $135.8517   $135.85   $135.85   $135.90  
  Purchase #5 $5.39   9.488%   $5.9014   $5.90   $5.90   $5.90  
  Purchase #6 $225.65   4.794%   $236.4677   $236.47   $236.45   $236.50  
  Purchase #7 $123.90   4.418%   $129.3739   $129.37   $129.35   $129.40  
  7 purchase totals = $908.47       $965.5424   $965.54   $965.45   $965.60