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 $13.88   5.333%   $14.6202   $14.62   $14.60   $14.60  
  Purchase #2 $194.77   6.232%   $206.9081   $206.91   $206.90   $206.90  
  Purchase #3 $205.55   3.348%   $212.4318   $212.43   $212.45   $212.40  
  Purchase #4 $226.33   8.466%   $245.4911   $245.49   $245.50   $245.50  
  Purchase #5 $50.26   13.636%   $57.1135   $57.11   $57.10   $57.10  
  Purchase #6 $160.87   10.308%   $177.4525   $177.45   $177.45   $177.50  
  Purchase #7 $170.57   11.572%   $190.3084   $190.31   $190.30   $190.30  
  7 purchase totals = $1,022.23       $1,104.3256   $1,104.32   $1,104.30   $1,104.30