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 $88.26   8.468%   $95.7339   $95.73   $95.75   $95.70  
  Purchase #2 $241.54   11.745%   $269.9089   $269.91   $269.90   $269.90  
  Purchase #3 $112.80   11.818%   $126.1307   $126.13   $126.15   $126.10  
  Purchase #4 $146.28   10.299%   $161.3454   $161.35   $161.35   $161.30  
  Purchase #5 $196.38   11.355%   $218.6789   $218.68   $218.70   $218.70  
  Purchase #6 $208.53   11.674%   $232.8738   $232.87   $232.85   $232.90  
  Purchase #7 $117.67   11.665%   $131.3962   $131.40   $131.40   $131.40  
  7 purchase totals = $1,111.46       $1,236.0678   $1,236.07   $1,236.10   $1,236.00