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 $88.87   6.847%   $94.9549   $94.95   $94.95   $95.00  
  Purchase #2 $162.76   5.386%   $171.5263   $171.53   $171.55   $171.50  
  Purchase #3 $16.62   8.351%   $18.0079   $18.01   $18.00   $18.00  
  Purchase #4 $244.38   4.103%   $254.4069   $254.41   $254.40   $254.40  
  Purchase #5 $249.47   11.593%   $278.3911   $278.39   $278.40   $278.40  
  Purchase #6 $107.48   10.352%   $118.6063   $118.61   $118.60   $118.60  
  Purchase #7 $125.61   4.528%   $131.2976   $131.30   $131.30   $131.30  
  7 purchase totals = $995.19       $1,067.1910   $1,067.20   $1,067.20   $1,067.20