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 $44.57   3.818%   $46.2717   $46.27   $46.25   $46.30  
  Purchase #2 $216.43   8.542%   $234.9175   $234.92   $234.90   $234.90  
  Purchase #3 $148.42   8.203%   $160.5949   $160.59   $160.60   $160.60  
  Purchase #4 $85.58   13.830%   $97.4157   $97.42   $97.40   $97.40  
  Purchase #5 $185.33   12.503%   $208.5018   $208.50   $208.50   $208.50  
  Purchase #6 $182.26   7.371%   $195.6944   $195.69   $195.70   $195.70  
  Purchase #7 $246.66   4.146%   $256.8865   $256.89   $256.90   $256.90  
  7 purchase totals = $1,109.25       $1,200.2825   $1,200.28   $1,200.25   $1,200.30