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 $57.34   9.785%   $62.9507   $62.95   $62.95   $63.00  
  Purchase #2 $178.36   9.299%   $194.9457   $194.95   $194.95   $194.90  
  Purchase #3 $226.89   5.816%   $240.0859   $240.09   $240.10   $240.10  
  Purchase #4 $155.82   10.676%   $172.4553   $172.46   $172.45   $172.50  
  Purchase #5 $129.55   13.133%   $146.5638   $146.56   $146.55   $146.60  
  Purchase #6 $117.39   8.248%   $127.0723   $127.07   $127.05   $127.10  
  Purchase #7 $133.32   3.493%   $137.9769   $137.98   $138.00   $138.00  
  7 purchase totals = $998.67       $1,082.0506   $1,082.06   $1,082.05   $1,082.20