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 $87.71   6.580%   $93.4813   $93.48   $93.50   $93.50  
  Purchase #2 $200.36   3.246%   $206.8637   $206.86   $206.85   $206.90  
  Purchase #3 $96.73   8.439%   $104.893   $104.89   $104.90   $104.90  
  Purchase #4 $170.87   13.720%   $194.3134   $194.31   $194.30   $194.30  
  Purchase #5 $228.87   6.396%   $243.5085   $243.51   $243.50   $243.50  
  Purchase #6 $151.64   6.671%   $161.7559   $161.76   $161.75   $161.80  
  Purchase #7 $115.47   5.782%   $122.1465   $122.15   $122.15   $122.10  
  7 purchase totals = $1,051.65       $1,126.9623   $1,126.96   $1,126.95   $1,127.00