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 $171.35   11.482%   $191.0244   $191.02   $191.00   $191.00  
  Purchase #2 $245.55   3.402%   $253.9036   $253.90   $253.90   $253.90  
  Purchase #3 $95.43   11.461%   $106.3672   $106.37   $106.35   $106.40  
  Purchase #4 $191.69   11.826%   $214.3593   $214.36   $214.35   $214.40  
  Purchase #5 $242.34   5.658%   $256.0516   $256.05   $256.05   $256.10  
  Purchase #6 $43.68   10.867%   $48.4267   $48.43   $48.45   $48.40  
  Purchase #7 $167.48   4.189%   $174.4957   $174.50   $174.50   $174.50  
  7 purchase totals = $1,157.52       $1,244.6285   $1,244.63   $1,244.60   $1,244.70