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 $194.66   5.494%   $205.3546   $205.35   $205.35   $205.40  
  Purchase #2 $58.86   4.328%   $61.4075   $61.41   $61.40   $61.40  
  Purchase #3 $93.27   8.322%   $101.0319   $101.03   $101.05   $101.00  
  Purchase #4 $185.82   5.653%   $196.3244   $196.32   $196.30   $196.30  
  Purchase #5 $160.70   10.233%   $177.1444   $177.14   $177.15   $177.10  
  Purchase #6 $118.40   6.461%   $126.0498   $126.05   $126.05   $126.00  
  Purchase #7 $111.86   7.309%   $120.0358   $120.04   $120.05   $120.00  
  7 purchase totals = $923.57       $987.3484   $987.34   $987.35   $987.20