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 $114.32   4.157%   $119.0723   $119.07   $119.05   $119.10  
  Purchase #2 $115.66   9.694%   $126.8721   $126.87   $126.85   $126.90  
  Purchase #3 $20.95   11.488%   $23.3567   $23.36   $23.35   $23.40  
  Purchase #4 $165.64   10.519%   $183.0637   $183.06   $183.05   $183.10  
  Purchase #5 $213.72   10.510%   $236.182   $236.18   $236.20   $236.20  
  Purchase #6 $102.29   11.134%   $113.679   $113.68   $113.70   $113.70  
  Purchase #7 $140.25   4.325%   $146.3158   $146.32   $146.30   $146.30  
  7 purchase totals = $872.83       $948.5416   $948.54   $948.50   $948.70