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 $201.52   11.570%   $224.8359   $224.84   $224.85   $224.80  
  Purchase #2 $205.98   13.781%   $234.3661   $234.37   $234.35   $234.40  
  Purchase #3 $102.53   9.719%   $112.4949   $112.49   $112.50   $112.50  
  Purchase #4 $59.71   11.674%   $66.6805   $66.68   $66.70   $66.70  
  Purchase #5 $198.27   8.213%   $214.5539   $214.55   $214.55   $214.60  
  Purchase #6 $8.48   5.221%   $8.9227   $8.92   $8.90   $8.90  
  Purchase #7 $9.34   11.145%   $10.3809   $10.38   $10.40   $10.40  
  7 purchase totals = $785.83       $872.2349   $872.23   $872.25   $872.30