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 $208.37   12.210%   $233.812   $233.81   $233.80   $233.80  
  Purchase #2 $119.55   4.631%   $125.0864   $125.09   $125.10   $125.10  
  Purchase #3 $218.41   12.591%   $245.91   $245.91   $245.90   $245.90  
  Purchase #4 $120.67   10.248%   $133.0363   $133.04   $133.05   $133.00  
  Purchase #5 $219.61   10.558%   $242.7964   $242.80   $242.80   $242.80  
  Purchase #6 $16.73   12.277%   $18.7839   $18.78   $18.80   $18.80  
  Purchase #7 $58.86   4.730%   $61.6441   $61.64   $61.65   $61.60  
  7 purchase totals = $962.20       $1,061.0691   $1,061.07   $1,061.10   $1,061.00