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 $202.92   5.481%   $214.042   $214.04   $214.05   $214.00  
  Purchase #2 $24.76   3.372%   $25.5949   $25.59   $25.60   $25.60  
  Purchase #3 $214.93   5.776%   $227.3444   $227.34   $227.35   $227.30  
  Purchase #4 $93.95   10.794%   $104.091   $104.09   $104.10   $104.10  
  Purchase #5 $91.79   4.232%   $95.6746   $95.67   $95.65   $95.70  
  Purchase #6 $63.78   4.491%   $66.6444   $66.64   $66.65   $66.60  
  Purchase #7 $182.69   6.305%   $194.2086   $194.21   $194.20   $194.20  
  7 purchase totals = $874.82       $927.5999   $927.58   $927.60   $927.50