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 $183.87   11.478%   $204.9746   $204.97   $204.95   $205.00  
  Purchase #2 $72.38   4.848%   $75.889   $75.89   $75.90   $75.90  
  Purchase #3 $157.78   6.789%   $168.4917   $168.49   $168.50   $168.50  
  Purchase #4 $204.88   10.168%   $225.7122   $225.71   $225.70   $225.70  
  Purchase #5 $119.75   9.747%   $131.422   $131.42   $131.40   $131.40  
  Purchase #6 $152.47   5.252%   $160.4777   $160.48   $160.50   $160.50  
  Purchase #7 $41.49   13.231%   $46.9795   $46.98   $47.00   $47.00  
  7 purchase totals = $932.62       $1,013.9467   $1,013.94   $1,013.95   $1,014.00