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 $23.28   7.457%   $25.016   $25.02   $25.00   $25.00  
  Purchase #2 $184.64   4.853%   $193.6006   $193.60   $193.60   $193.60  
  Purchase #3 $100.53   7.137%   $107.7048   $107.70   $107.70   $107.70  
  Purchase #4 $64.90   13.752%   $73.825   $73.83   $73.85   $73.80  
  Purchase #5 $181.78   9.551%   $199.1418   $199.14   $199.15   $199.10  
  Purchase #6 $194.54   7.664%   $209.4495   $209.45   $209.45   $209.40  
  Purchase #7 $139.26   8.695%   $151.3687   $151.37   $151.35   $151.40  
  7 purchase totals = $888.93       $960.1064   $960.11   $960.10   $960.00