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 $67.95   12.776%   $76.6313   $76.63   $76.65   $76.60  
  Purchase #2 $132.58   12.757%   $149.4932   $149.49   $149.50   $149.50  
  Purchase #3 $195.31   7.116%   $209.2083   $209.21   $209.20   $209.20  
  Purchase #4 $76.79   12.290%   $86.2275   $86.23   $86.25   $86.20  
  Purchase #5 $149.83   6.615%   $159.7413   $159.74   $159.75   $159.70  
  Purchase #6 $202.57   9.807%   $222.436   $222.44   $222.45   $222.40  
  Purchase #7 $35.98   12.192%   $40.3667   $40.37   $40.35   $40.40  
  7 purchase totals = $861.01       $944.1043   $944.11   $944.15   $944.00