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 $34.86   4.250%   $36.3416   $36.34   $36.35   $36.30  
  Purchase #2 $186.73   5.196%   $196.4325   $196.43   $196.45   $196.40  
  Purchase #3 $236.88   3.206%   $244.4744   $244.47   $244.45   $244.50  
  Purchase #4 $197.51   13.740%   $224.6479   $224.65   $224.65   $224.60  
  Purchase #5 $129.40   13.277%   $146.5804   $146.58   $146.60   $146.60  
  Purchase #6 $219.75   13.418%   $249.2361   $249.24   $249.25   $249.20  
  Purchase #7 $6.49   5.793%   $6.866   $6.87   $6.85   $6.90  
  7 purchase totals = $1,011.62       $1,104.5789   $1,104.58   $1,104.60   $1,104.50