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 $104.61   9.245%   $114.2812   $114.28   $114.30   $114.30  
  Purchase #2 $53.47   7.511%   $57.4861   $57.49   $57.50   $57.50  
  Purchase #3 $146.70   11.259%   $163.217   $163.22   $163.20   $163.20  
  Purchase #4 $171.98   3.345%   $177.7327   $177.73   $177.75   $177.70  
  Purchase #5 $232.48   12.700%   $262.005   $262.01   $262.00   $262.00  
  Purchase #6 $195.38   10.156%   $215.2228   $215.22   $215.20   $215.20  
  Purchase #7 $100.35   11.770%   $112.1612   $112.16   $112.15   $112.20  
  7 purchase totals = $1,004.97       $1,102.1060   $1,102.11   $1,102.10   $1,102.10