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 $148.57   9.861%   $163.2205   $163.22   $163.20   $163.20  
  Purchase #2 $12.90   10.440%   $14.2468   $14.25   $14.25   $14.20  
  Purchase #3 $155.71   7.467%   $167.3369   $167.34   $167.35   $167.30  
  Purchase #4 $125.31   6.160%   $133.0291   $133.03   $133.05   $133.00  
  Purchase #5 $249.33   5.151%   $262.173   $262.17   $262.15   $262.20  
  Purchase #6 $122.37   7.853%   $131.9797   $131.98   $132.00   $132.00  
  Purchase #7 $194.85   3.726%   $202.1101   $202.11   $202.10   $202.10  
  7 purchase totals = $1,009.04       $1,074.0961   $1,074.10   $1,074.10   $1,074.00