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 $93.72   3.769%   $97.2523   $97.25   $97.25   $97.30  
  Purchase #2 $162.60   9.644%   $178.2811   $178.28   $178.30   $178.30  
  Purchase #3 $155.79   11.631%   $173.9099   $173.91   $173.90   $173.90  
  Purchase #4 $216.55   4.195%   $225.6343   $225.63   $225.65   $225.60  
  Purchase #5 $193.62   7.805%   $208.732   $208.73   $208.75   $208.70  
  Purchase #6 $114.90   4.352%   $119.9004   $119.90   $119.90   $119.90  
  Purchase #7 $191.97   9.523%   $210.2513   $210.25   $210.25   $210.30  
  7 purchase totals = $1,129.15       $1,213.9613   $1,213.95   $1,214.00   $1,214.00