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 $162.97   8.614%   $177.0082   $177.01   $177.00   $177.00  
  Purchase #2 $173.46   11.813%   $193.9508   $193.95   $193.95   $194.00  
  Purchase #3 $78.76   4.603%   $82.3853   $82.39   $82.40   $82.40  
  Purchase #4 $103.95   7.769%   $112.0259   $112.03   $112.05   $112.00  
  Purchase #5 $224.85   11.519%   $250.7505   $250.75   $250.75   $250.80  
  Purchase #6 $15.86   12.587%   $17.8563   $17.86   $17.85   $17.90  
  Purchase #7 $96.83   11.121%   $107.5985   $107.60   $107.60   $107.60  
  7 purchase totals = $856.68       $941.5755   $941.59   $941.60   $941.70