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 $176.97   12.746%   $199.5266   $199.53   $199.55   $199.50  
  Purchase #2 $41.51   3.699%   $43.0455   $43.05   $43.05   $43.00  
  Purchase #3 $229.90   6.348%   $244.4941   $244.49   $244.50   $244.50  
  Purchase #4 $137.72   7.108%   $147.5091   $147.51   $147.50   $147.50  
  Purchase #5 $191.50   6.627%   $204.1907   $204.19   $204.20   $204.20  
  Purchase #6 $78.41   8.804%   $85.3132   $85.31   $85.30   $85.30  
  Purchase #7 $190.53   9.794%   $209.1905   $209.19   $209.20   $209.20  
  7 purchase totals = $1,046.54       $1,133.2697   $1,133.27   $1,133.30   $1,133.20