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 $60.49   4.561%   $63.2489   $63.25   $63.25   $63.20  
  Purchase #2 $212.59   10.480%   $234.8694   $234.87   $234.85   $234.90  
  Purchase #3 $87.38   11.783%   $97.676   $97.68   $97.70   $97.70  
  Purchase #4 $224.94   13.218%   $254.6726   $254.67   $254.65   $254.70  
  Purchase #5 $92.54   11.667%   $103.3366   $103.34   $103.35   $103.30  
  Purchase #6 $109.40   12.548%   $123.1275   $123.13   $123.15   $123.10  
  Purchase #7 $49.74   5.804%   $52.6269   $52.63   $52.65   $52.60  
  7 purchase totals = $837.08       $929.5579   $929.57   $929.60   $929.50