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 $88.40   10.807%   $97.9534   $97.95   $97.95   $98.00  
  Purchase #2 $70.38   12.195%   $78.9628   $78.96   $78.95   $79.00  
  Purchase #3 $25.47   13.189%   $28.8292   $28.83   $28.85   $28.80  
  Purchase #4 $216.77   4.589%   $226.7176   $226.72   $226.70   $226.70  
  Purchase #5 $226.85   5.322%   $238.923   $238.92   $238.90   $238.90  
  Purchase #6 $250.99   8.105%   $271.3327   $271.33   $271.35   $271.30  
  Purchase #7 $73.41   13.463%   $83.2932   $83.29   $83.30   $83.30  
  7 purchase totals = $952.27       $1,026.0119   $1,026.00   $1,026.00   $1,026.00