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 $154.55   5.297%   $162.7365   $162.74   $162.75   $162.70  
  Purchase #2 $158.97   11.691%   $177.5552   $177.56   $177.55   $177.60  
  Purchase #3 $54.91   13.634%   $62.3964   $62.40   $62.40   $62.40  
  Purchase #4 $93.37   4.319%   $97.4027   $97.40   $97.40   $97.40  
  Purchase #5 $201.76   7.754%   $217.4045   $217.40   $217.40   $217.40  
  Purchase #6 $174.49   12.268%   $195.8964   $195.90   $195.90   $195.90  
  Purchase #7 $170.82   10.357%   $188.5118   $188.51   $188.50   $188.50  
  7 purchase totals = $1,008.87       $1,101.9035   $1,101.91   $1,101.90   $1,101.90