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 $113.87   11.447%   $126.9047   $126.90   $126.90   $126.90  
  Purchase #2 $49.96   9.540%   $54.7262   $54.73   $54.75   $54.70  
  Purchase #3 $24.89   5.127%   $26.1661   $26.17   $26.15   $26.20  
  Purchase #4 $61.37   8.650%   $66.6785   $66.68   $66.70   $66.70  
  Purchase #5 $206.97   3.278%   $213.7545   $213.75   $213.75   $213.80  
  Purchase #6 $18.34   4.665%   $19.1956   $19.20   $19.20   $19.20  
  Purchase #7 $198.89   13.230%   $225.2031   $225.20   $225.20   $225.20  
  7 purchase totals = $674.29       $732.6287   $732.63   $732.65   $732.70