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 $68.44   10.696%   $75.7603   $75.76   $75.75   $75.80  
  Purchase #2 $156.65   3.745%   $162.5165   $162.52   $162.50   $162.50  
  Purchase #3 $66.76   9.105%   $72.8385   $72.84   $72.85   $72.80  
  Purchase #4 $209.69   11.546%   $233.9008   $233.90   $233.90   $233.90  
  Purchase #5 $233.66   8.187%   $252.7897   $252.79   $252.80   $252.80  
  Purchase #6 $54.37   12.563%   $61.2005   $61.20   $61.20   $61.20  
  Purchase #7 $247.54   5.302%   $260.6646   $260.66   $260.65   $260.70  
  7 purchase totals = $1,037.11       $1,119.6709   $1,119.67   $1,119.65   $1,119.70