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 $12.34   13.798%   $14.0427   $14.04   $14.05   $14.00  
  Purchase #2 $58.68   10.522%   $64.8543   $64.85   $64.85   $64.90  
  Purchase #3 $181.81   5.164%   $191.1987   $191.20   $191.20   $191.20  
  Purchase #4 $250.32   4.759%   $262.2327   $262.23   $262.25   $262.20  
  Purchase #5 $61.88   13.349%   $70.1404   $70.14   $70.15   $70.10  
  Purchase #6 $248.43   7.834%   $267.892   $267.89   $267.90   $267.90  
  Purchase #7 $232.78   6.669%   $248.3041   $248.30   $248.30   $248.30  
  7 purchase totals = $1,046.24       $1,118.6649   $1,118.65   $1,118.70   $1,118.60