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 $233.47   3.583%   $241.8352   $241.84   $241.85   $241.80  
  Purchase #2 $220.29   13.233%   $249.441   $249.44   $249.45   $249.40  
  Purchase #3 $227.97   8.123%   $246.488   $246.49   $246.50   $246.50  
  Purchase #4 $94.91   7.312%   $101.8498   $101.85   $101.85   $101.80  
  Purchase #5 $238.32   12.543%   $268.2125   $268.21   $268.20   $268.20  
  Purchase #6 $202.91   4.178%   $211.3876   $211.39   $211.40   $211.40  
  Purchase #7 $167.36   4.476%   $174.851   $174.85   $174.85   $174.90  
  7 purchase totals = $1,385.23       $1,494.0651   $1,494.07   $1,494.10   $1,494.00