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 $61.57   5.487%   $64.9483   $64.95   $64.95   $64.90  
  Purchase #2 $201.98   10.736%   $223.6646   $223.66   $223.65   $223.70  
  Purchase #3 $78.49   12.592%   $88.3735   $88.37   $88.35   $88.40  
  Purchase #4 $239.56   10.735%   $265.2768   $265.28   $265.30   $265.30  
  Purchase #5 $85.43   9.798%   $93.8004   $93.80   $93.80   $93.80  
  Purchase #6 $111.56   5.589%   $117.7951   $117.80   $117.80   $117.80  
  Purchase #7 $93.81   9.272%   $102.5081   $102.51   $102.50   $102.50  
  7 purchase totals = $872.40       $956.3668   $956.37   $956.35   $956.40