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 $181.28   6.275%   $192.6553   $192.66   $192.65   $192.70  
  Purchase #2 $104.88   10.273%   $115.6543   $115.65   $115.65   $115.70  
  Purchase #3 $89.63   3.601%   $92.8576   $92.86   $92.85   $92.90  
  Purchase #4 $179.52   3.239%   $185.3347   $185.33   $185.35   $185.30  
  Purchase #5 $130.99   5.105%   $137.677   $137.68   $137.70   $137.70  
  Purchase #6 $217.44   12.263%   $244.1047   $244.10   $244.10   $244.10  
  Purchase #7 $93.97   10.707%   $104.0314   $104.03   $104.05   $104.00  
  7 purchase totals = $997.71       $1,072.3150   $1,072.31   $1,072.35   $1,072.40