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 $174.76   6.268%   $185.714   $185.71   $185.70   $185.70  
  Purchase #2 $37.57   10.847%   $41.6452   $41.65   $41.65   $41.60  
  Purchase #3 $249.75   7.403%   $268.239   $268.24   $268.25   $268.20  
  Purchase #4 $244.98   6.547%   $261.0188   $261.02   $261.00   $261.00  
  Purchase #5 $152.78   10.186%   $168.3422   $168.34   $168.35   $168.30  
  Purchase #6 $62.55   8.598%   $67.928   $67.93   $67.95   $67.90  
  Purchase #7 $135.49   13.152%   $153.3096   $153.31   $153.30   $153.30  
  7 purchase totals = $1,057.88       $1,146.1968   $1,146.20   $1,146.20   $1,146.00