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 $117.67   6.871%   $125.7551   $125.76   $125.75   $125.80  
  Purchase #2 $89.36   6.295%   $94.9852   $94.99   $95.00   $95.00  
  Purchase #3 $158.81   10.744%   $175.8725   $175.87   $175.85   $175.90  
  Purchase #4 $26.44   12.519%   $29.75   $29.75   $29.75   $29.80  
  Purchase #5 $42.51   10.637%   $47.0318   $47.03   $47.05   $47.00  
  Purchase #6 $232.75   5.856%   $246.3798   $246.38   $246.40   $246.40  
  Purchase #7 $204.35   9.170%   $223.0889   $223.09   $223.10   $223.10  
  7 purchase totals = $871.89       $942.8633   $942.87   $942.90   $943.00