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 $59.38   4.664%   $62.1495   $62.15   $62.15   $62.10  
  Purchase #2 $217.26   7.175%   $232.8484   $232.85   $232.85   $232.80  
  Purchase #3 $160.99   9.330%   $176.0104   $176.01   $176.00   $176.00  
  Purchase #4 $48.35   11.653%   $53.9842   $53.98   $54.00   $54.00  
  Purchase #5 $112.87   5.117%   $118.6456   $118.65   $118.65   $118.60  
  Purchase #6 $144.87   3.730%   $150.2737   $150.27   $150.25   $150.30  
  Purchase #7 $132.86   5.390%   $140.0212   $140.02   $140.00   $140.00  
  7 purchase totals = $876.58       $933.9330   $933.93   $933.90   $933.80