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 $91.68   4.287%   $95.6103   $95.61   $95.60   $95.60  
  Purchase #2 $157.33   7.778%   $169.5671   $169.57   $169.55   $169.60  
  Purchase #3 $50.33   11.179%   $55.9564   $55.96   $55.95   $56.00  
  Purchase #4 $234.76   4.361%   $244.9979   $245.00   $245.00   $245.00  
  Purchase #5 $137.44   12.128%   $154.1087   $154.11   $154.10   $154.10  
  Purchase #6 $199.68   4.557%   $208.7794   $208.78   $208.80   $208.80  
  Purchase #7 $143.71   3.645%   $148.9482   $148.95   $148.95   $148.90  
  7 purchase totals = $1,014.93       $1,077.9680   $1,077.98   $1,077.95   $1,078.00