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 $55.25   13.525%   $62.7226   $62.72   $62.70   $62.70  
  Purchase #2 $158.48   7.118%   $169.7606   $169.76   $169.75   $169.80  
  Purchase #3 $249.44   8.605%   $270.9043   $270.90   $270.90   $270.90  
  Purchase #4 $207.51   12.224%   $232.876   $232.88   $232.90   $232.90  
  Purchase #5 $59.86   5.127%   $62.929   $62.93   $62.95   $62.90  
  Purchase #6 $171.30   8.124%   $185.2164   $185.22   $185.20   $185.20  
  Purchase #7 $114.71   5.647%   $121.1877   $121.19   $121.20   $121.20  
  7 purchase totals = $1,016.55       $1,105.5966   $1,105.60   $1,105.60   $1,105.60