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 $191.86   6.366%   $204.0738   $204.07   $204.05   $204.10  
  Purchase #2 $207.62   9.203%   $226.7273   $226.73   $226.75   $226.70  
  Purchase #3 $89.83   5.127%   $94.4356   $94.44   $94.45   $94.40  
  Purchase #4 $183.29   6.267%   $194.7768   $194.78   $194.80   $194.80  
  Purchase #5 $167.45   5.593%   $176.8155   $176.82   $176.80   $176.80  
  Purchase #6 $234.32   4.248%   $244.2739   $244.27   $244.25   $244.30  
  Purchase #7 $112.77   9.391%   $123.3602   $123.36   $123.35   $123.40  
  7 purchase totals = $1,187.14       $1,264.4631   $1,264.47   $1,264.45   $1,264.50