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 $88.63   6.758%   $94.6196   $94.62   $94.60   $94.60  
  Purchase #2 $162.43   6.829%   $173.5223   $173.52   $173.50   $173.50  
  Purchase #3 $98.91   5.834%   $104.6804   $104.68   $104.70   $104.70  
  Purchase #4 $165.70   5.212%   $174.3363   $174.34   $174.35   $174.30  
  Purchase #5 $213.75   6.248%   $227.1051   $227.11   $227.10   $227.10  
  Purchase #6 $176.38   10.489%   $194.8805   $194.88   $194.90   $194.90  
  Purchase #7 $201.52   8.394%   $218.4356   $218.44   $218.45   $218.40  
  7 purchase totals = $1,107.32       $1,187.5798   $1,187.59   $1,187.60   $1,187.50