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 $68.45   7.496%   $73.581   $73.58   $73.60   $73.60  
  Purchase #2 $104.63   5.377%   $110.256   $110.26   $110.25   $110.30  
  Purchase #3 $60.86   3.738%   $63.1349   $63.13   $63.15   $63.10  
  Purchase #4 $97.74   13.453%   $110.889   $110.89   $110.90   $110.90  
  Purchase #5 $110.55   13.270%   $125.22   $125.22   $125.20   $125.20  
  Purchase #6 $86.67   3.359%   $89.5812   $89.58   $89.60   $89.60  
  Purchase #7 $109.37   4.676%   $114.4841   $114.48   $114.50   $114.50  
  7 purchase totals = $638.27       $687.1462   $687.14   $687.20   $687.20