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 $118.51   5.823%   $125.4108   $125.41   $125.40   $125.40  
  Purchase #2 $211.39   12.374%   $237.5474   $237.55   $237.55   $237.50  
  Purchase #3 $51.85   6.200%   $55.0647   $55.06   $55.05   $55.10  
  Purchase #4 $226.53   3.687%   $234.8822   $234.88   $234.90   $234.90  
  Purchase #5 $76.58   11.458%   $85.3545   $85.35   $85.35   $85.40  
  Purchase #6 $238.60   6.422%   $253.9229   $253.92   $253.90   $253.90  
  Purchase #7 $199.85   6.184%   $212.2087   $212.21   $212.20   $212.20  
  7 purchase totals = $1,123.31       $1,204.3912   $1,204.38   $1,204.35   $1,204.40