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 $47.89   5.305%   $50.4306   $50.43   $50.45   $50.40  
  Purchase #2 $163.66   5.727%   $173.0328   $173.03   $173.05   $173.00  
  Purchase #3 $112.91   8.159%   $122.1223   $122.12   $122.10   $122.10  
  Purchase #4 $172.87   3.800%   $179.4391   $179.44   $179.45   $179.40  
  Purchase #5 $217.29   4.320%   $226.6769   $226.68   $226.70   $226.70  
  Purchase #6 $135.41   5.673%   $143.0918   $143.09   $143.10   $143.10  
  Purchase #7 $152.74   10.211%   $168.3363   $168.34   $168.35   $168.30  
  7 purchase totals = $1,002.77       $1,063.1298   $1,063.13   $1,063.20   $1,063.00