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 $44.75   3.210%   $46.1865   $46.19   $46.20   $46.20  
  Purchase #2 $86.95   10.297%   $95.9032   $95.90   $95.90   $95.90  
  Purchase #3 $15.52   4.282%   $16.1846   $16.18   $16.20   $16.20  
  Purchase #4 $122.37   5.616%   $129.2423   $129.24   $129.25   $129.20  
  Purchase #5 $44.69   7.749%   $48.153   $48.15   $48.15   $48.20  
  Purchase #6 $111.29   3.874%   $115.6014   $115.60   $115.60   $115.60  
  Purchase #7 $249.95   12.871%   $282.1211   $282.12   $282.10   $282.10  
  7 purchase totals = $675.52       $733.3921   $733.38   $733.40   $733.40