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 $43.59   5.691%   $46.0707   $46.07   $46.05   $46.10  
  Purchase #2 $22.46   6.525%   $23.9255   $23.93   $23.95   $23.90  
  Purchase #3 $86.92   12.676%   $97.938   $97.94   $97.95   $97.90  
  Purchase #4 $167.73   11.311%   $186.7019   $186.70   $186.70   $186.70  
  Purchase #5 $157.57   7.636%   $169.602   $169.60   $169.60   $169.60  
  Purchase #6 $129.96   8.462%   $140.9572   $140.96   $140.95   $141.00  
  Purchase #7 $53.99   9.497%   $59.1174   $59.12   $59.10   $59.10  
  7 purchase totals = $662.22       $724.3127   $724.32   $724.30   $724.30