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 $72.81   12.573%   $81.9644   $81.96   $81.95   $82.00  
  Purchase #2 $181.71   7.287%   $194.9512   $194.95   $194.95   $195.00  
  Purchase #3 $189.35   13.853%   $215.5807   $215.58   $215.60   $215.60  
  Purchase #4 $183.91   13.804%   $209.2969   $209.30   $209.30   $209.30  
  Purchase #5 $116.66   7.227%   $125.091   $125.09   $125.10   $125.10  
  Purchase #6 $96.86   7.640%   $104.2601   $104.26   $104.25   $104.30  
  Purchase #7 $208.99   8.676%   $227.122   $227.12   $227.10   $227.10  
  7 purchase totals = $1,050.29       $1,158.2663   $1,158.26   $1,158.25   $1,158.40