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 $62.51   8.342%   $67.7246   $67.72   $67.70   $67.70  
  Purchase #2 $214.53   11.768%   $239.7759   $239.78   $239.80   $239.80  
  Purchase #3 $175.39   11.296%   $195.2021   $195.20   $195.20   $195.20  
  Purchase #4 $70.70   10.858%   $78.3766   $78.38   $78.40   $78.40  
  Purchase #5 $135.33   13.205%   $153.2003   $153.20   $153.20   $153.20  
  Purchase #6 $94.64   7.490%   $101.7285   $101.73   $101.75   $101.70  
  Purchase #7 $208.82   7.560%   $224.6068   $224.61   $224.60   $224.60  
  7 purchase totals = $961.92       $1,060.6148   $1,060.62   $1,060.65   $1,060.60