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 $114.35   10.156%   $125.9634   $125.96   $125.95   $126.00  
  Purchase #2 $147.89   12.793%   $166.8096   $166.81   $166.80   $166.80  
  Purchase #3 $105.48   13.282%   $119.4899   $119.49   $119.50   $119.50  
  Purchase #4 $149.72   9.692%   $164.2309   $164.23   $164.25   $164.20  
  Purchase #5 $109.73   13.339%   $124.3669   $124.37   $124.35   $124.40  
  Purchase #6 $93.76   4.703%   $98.1695   $98.17   $98.15   $98.20  
  Purchase #7 $114.26   7.681%   $123.0363   $123.04   $123.05   $123.00  
  7 purchase totals = $835.19       $922.0665   $922.07   $922.05   $922.10