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 $116.89   7.604%   $125.7783   $125.78   $125.80   $125.80  
  Purchase #2 $212.26   6.397%   $225.8383   $225.84   $225.85   $225.80  
  Purchase #3 $187.45   4.494%   $195.874   $195.87   $195.85   $195.90  
  Purchase #4 $115.50   3.372%   $119.3947   $119.39   $119.40   $119.40  
  Purchase #5 $66.87   10.796%   $74.0893   $74.09   $74.10   $74.10  
  Purchase #6 $183.33   12.489%   $206.2261   $206.23   $206.25   $206.20  
  Purchase #7 $104.53   9.735%   $114.706   $114.71   $114.70   $114.70  
  7 purchase totals = $986.83       $1,061.9067   $1,061.91   $1,061.95   $1,061.90