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 $93.36   8.874%   $101.6448   $101.64   $101.65   $101.60  
  Purchase #2 $43.83   4.388%   $45.7533   $45.75   $45.75   $45.80  
  Purchase #3 $26.90   10.207%   $29.6457   $29.65   $29.65   $29.60  
  Purchase #4 $158.63   9.704%   $174.0235   $174.02   $174.00   $174.00  
  Purchase #5 $92.28   5.326%   $97.1948   $97.19   $97.20   $97.20  
  Purchase #6 $238.79   5.406%   $251.699   $251.70   $251.70   $251.70  
  Purchase #7 $58.57   5.347%   $61.7017   $61.70   $61.70   $61.70  
  7 purchase totals = $712.36       $761.6628   $761.65   $761.65   $761.60