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 $54.99   13.830%   $62.5951   $62.60   $62.60   $62.60  
  Purchase #2 $171.49   12.791%   $193.4253   $193.43   $193.45   $193.40  
  Purchase #3 $245.76   4.172%   $256.0131   $256.01   $256.00   $256.00  
  Purchase #4 $156.91   12.749%   $176.9145   $176.91   $176.90   $176.90  
  Purchase #5 $178.47   4.534%   $186.5618   $186.56   $186.55   $186.60  
  Purchase #6 $155.97   11.804%   $174.3807   $174.38   $174.40   $174.40  
  Purchase #7 $155.99   3.851%   $161.9972   $162.00   $162.00   $162.00  
  7 purchase totals = $1,119.58       $1,211.8877   $1,211.89   $1,211.90   $1,211.90