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 $195.80   7.787%   $211.0469   $211.05   $211.05   $211.00  
  Purchase #2 $244.97   7.286%   $262.8185   $262.82   $262.80   $262.80  
  Purchase #3 $20.69   11.250%   $23.0176   $23.02   $23.00   $23.00  
  Purchase #4 $194.44   6.732%   $207.5297   $207.53   $207.55   $207.50  
  Purchase #5 $9.45   7.613%   $10.1694   $10.17   $10.15   $10.20  
  Purchase #6 $41.63   12.168%   $46.6955   $46.70   $46.70   $46.70  
  Purchase #7 $24.30   13.507%   $27.5822   $27.58   $27.60   $27.60  
  7 purchase totals = $731.28       $788.8598   $788.87   $788.85   $788.80