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 $106.34   5.461%   $112.1472   $112.15   $112.15   $112.10  
  Purchase #2 $71.95   3.395%   $74.3927   $74.39   $74.40   $74.40  
  Purchase #3 $10.96   6.432%   $11.6649   $11.66   $11.65   $11.70  
  Purchase #4 $234.81   11.781%   $262.473   $262.47   $262.45   $262.50  
  Purchase #5 $102.99   9.113%   $112.3755   $112.38   $112.40   $112.40  
  Purchase #6 $140.75   7.249%   $150.953   $150.95   $150.95   $151.00  
  Purchase #7 $213.47   11.206%   $237.3914   $237.39   $237.40   $237.40  
  7 purchase totals = $881.27       $961.3977   $961.39   $961.40   $961.50