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 $67.50   11.863%   $75.5075   $75.51   $75.50   $75.50  
  Purchase #2 $181.31   7.356%   $194.6472   $194.65   $194.65   $194.60  
  Purchase #3 $59.64   7.525%   $64.1279   $64.13   $64.15   $64.10  
  Purchase #4 $227.98   5.559%   $240.6534   $240.65   $240.65   $240.70  
  Purchase #5 $34.93   13.478%   $39.6379   $39.64   $39.65   $39.60  
  Purchase #6 $80.89   13.654%   $91.9347   $91.93   $91.95   $91.90  
  Purchase #7 $211.31   8.450%   $229.1657   $229.17   $229.15   $229.20  
  7 purchase totals = $863.56       $935.6743   $935.68   $935.70   $935.60