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 $88.34   8.192%   $95.5768   $95.58   $95.60   $95.60  
  Purchase #2 $162.59   9.543%   $178.106   $178.11   $178.10   $178.10  
  Purchase #3 $104.95   7.413%   $112.7299   $112.73   $112.75   $112.70  
  Purchase #4 $25.31   7.396%   $27.1819   $27.18   $27.20   $27.20  
  Purchase #5 $199.46   6.185%   $211.7966   $211.80   $211.80   $211.80  
  Purchase #6 $191.64   5.525%   $202.2281   $202.23   $202.25   $202.20  
  Purchase #7 $26.85   3.289%   $27.7331   $27.73   $27.75   $27.70  
  7 purchase totals = $799.14       $855.3524   $855.36   $855.45   $855.30