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 $41.68   7.541%   $44.8231   $44.82   $44.80   $44.80  
  Purchase #2 $117.44   13.282%   $133.0384   $133.04   $133.05   $133.00  
  Purchase #3 $233.72   13.726%   $265.8004   $265.80   $265.80   $265.80  
  Purchase #4 $191.61   7.484%   $205.9501   $205.95   $205.95   $206.00  
  Purchase #5 $223.76   9.243%   $244.4421   $244.44   $244.45   $244.40  
  Purchase #6 $183.73   6.730%   $196.095   $196.10   $196.10   $196.10  
  Purchase #7 $112.42   5.816%   $118.9583   $118.96   $118.95   $119.00  
  7 purchase totals = $1,104.36       $1,209.1074   $1,209.11   $1,209.10   $1,209.10