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 $144.62   7.832%   $155.9466   $155.95   $155.95   $155.90  
  Purchase #2 $215.87   3.279%   $222.9484   $222.95   $222.95   $222.90  
  Purchase #3 $184.30   13.805%   $209.7426   $209.74   $209.75   $209.70  
  Purchase #4 $31.74   13.566%   $36.0458   $36.05   $36.05   $36.00  
  Purchase #5 $164.90   12.334%   $185.2388   $185.24   $185.25   $185.20  
  Purchase #6 $245.65   8.464%   $266.4418   $266.44   $266.45   $266.40  
  Purchase #7 $76.25   13.287%   $86.3813   $86.38   $86.40   $86.40  
  7 purchase totals = $1,063.33       $1,162.7453   $1,162.75   $1,162.80   $1,162.50