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 $221.27   6.632%   $235.9446   $235.94   $235.95   $235.90  
  Purchase #2 $8.93   10.426%   $9.861   $9.86   $9.85   $9.90  
  Purchase #3 $109.82   8.473%   $119.125   $119.13   $119.15   $119.10  
  Purchase #4 $202.78   5.388%   $213.7058   $213.71   $213.70   $213.70  
  Purchase #5 $246.66   8.565%   $267.7864   $267.79   $267.80   $267.80  
  Purchase #6 $189.37   5.515%   $199.8138   $199.81   $199.80   $199.80  
  Purchase #7 $66.82   9.343%   $73.063   $73.06   $73.05   $73.10  
  7 purchase totals = $1,045.65       $1,119.2996   $1,119.30   $1,119.30   $1,119.30