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 $117.59   6.349%   $125.0558   $125.06   $125.05   $125.10  
  Purchase #2 $143.44   7.804%   $154.6341   $154.63   $154.65   $154.60  
  Purchase #3 $162.64   10.564%   $179.8213   $179.82   $179.80   $179.80  
  Purchase #4 $91.68   3.396%   $94.7935   $94.79   $94.80   $94.80  
  Purchase #5 $17.87   4.534%   $18.6802   $18.68   $18.70   $18.70  
  Purchase #6 $148.63   6.254%   $157.9253   $157.93   $157.95   $157.90  
  Purchase #7 $90.35   6.222%   $95.9716   $95.97   $95.95   $96.00  
  7 purchase totals = $772.20       $826.8818   $826.88   $826.90   $826.90