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 $42.95   8.109%   $46.4328   $46.43   $46.45   $46.40  
  Purchase #2 $218.46   7.320%   $234.4513   $234.45   $234.45   $234.50  
  Purchase #3 $8.91   3.797%   $9.2483   $9.25   $9.25   $9.20  
  Purchase #4 $239.66   8.209%   $259.3337   $259.33   $259.35   $259.30  
  Purchase #5 $205.51   3.388%   $212.4727   $212.47   $212.45   $212.50  
  Purchase #6 $181.50   13.163%   $205.3908   $205.39   $205.40   $205.40  
  Purchase #7 $183.55   8.832%   $199.7611   $199.76   $199.75   $199.80  
  7 purchase totals = $1,080.54       $1,167.0907   $1,167.08   $1,167.10   $1,167.10