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 $183.26   6.396%   $194.9813   $194.98   $195.00   $195.00  
  Purchase #2 $188.60   10.363%   $208.1446   $208.14   $208.15   $208.10  
  Purchase #3 $5.43   10.325%   $5.9906   $5.99   $6.00   $6.00  
  Purchase #4 $82.48   5.590%   $87.0906   $87.09   $87.10   $87.10  
  Purchase #5 $108.61   6.423%   $115.586   $115.59   $115.60   $115.60  
  Purchase #6 $37.36   8.593%   $40.5703   $40.57   $40.55   $40.60  
  Purchase #7 $216.62   7.580%   $233.0398   $233.04   $233.05   $233.00  
  7 purchase totals = $822.36       $885.4032   $885.40   $885.45   $885.40