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 $241.87   10.742%   $267.8517   $267.85   $267.85   $267.90  
  Purchase #2 $88.51   10.141%   $97.4858   $97.49   $97.50   $97.50  
  Purchase #3 $183.41   3.769%   $190.3227   $190.32   $190.30   $190.30  
  Purchase #4 $221.87   10.679%   $245.5635   $245.56   $245.55   $245.60  
  Purchase #5 $97.68   12.547%   $109.9359   $109.94   $109.95   $109.90  
  Purchase #6 $186.50   11.310%   $207.5932   $207.59   $207.60   $207.60  
  Purchase #7 $76.31   9.139%   $83.284   $83.28   $83.30   $83.30  
  7 purchase totals = $1,096.15       $1,202.0368   $1,202.03   $1,202.05   $1,202.10