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 $157.43   10.501%   $173.9617   $173.96   $173.95   $174.00  
  Purchase #2 $176.62   4.767%   $185.0395   $185.04   $185.05   $185.00  
  Purchase #3 $9.94   10.714%   $11.005   $11.01   $11.00   $11.00  
  Purchase #4 $43.71   11.393%   $48.6899   $48.69   $48.70   $48.70  
  Purchase #5 $144.54   7.427%   $155.275   $155.28   $155.30   $155.30  
  Purchase #6 $158.39   11.266%   $176.2342   $176.23   $176.25   $176.20  
  Purchase #7 $222.53   10.482%   $245.8556   $245.86   $245.85   $245.90  
  7 purchase totals = $913.16       $996.0609   $996.07   $996.10   $996.10