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 $187.38   4.326%   $195.4861   $195.49   $195.50   $195.50  
  Purchase #2 $21.42   13.227%   $24.2532   $24.25   $24.25   $24.30  
  Purchase #3 $26.75   13.122%   $30.2601   $30.26   $30.25   $30.30  
  Purchase #4 $67.60   5.574%   $71.368   $71.37   $71.35   $71.40  
  Purchase #5 $170.47   4.867%   $178.7668   $178.77   $178.75   $178.80  
  Purchase #6 $244.48   8.475%   $265.1997   $265.20   $265.20   $265.20  
  Purchase #7 $203.89   3.467%   $210.9589   $210.96   $210.95   $211.00  
  7 purchase totals = $921.99       $976.2928   $976.30   $976.25   $976.50