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 $175.53   13.379%   $199.0142   $199.01   $199.00   $199.00  
  Purchase #2 $67.43   9.518%   $73.848   $73.85   $73.85   $73.80  
  Purchase #3 $75.84   4.296%   $79.0981   $79.10   $79.10   $79.10  
  Purchase #4 $179.36   7.606%   $193.0021   $193.00   $193.00   $193.00  
  Purchase #5 $150.84   4.768%   $158.0321   $158.03   $158.05   $158.00  
  Purchase #6 $109.98   13.586%   $124.9219   $124.92   $124.90   $124.90  
  Purchase #7 $198.41   7.356%   $213.005   $213.01   $213.00   $213.00  
  7 purchase totals = $957.39       $1,040.9214   $1,040.92   $1,040.90   $1,040.80