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 $196.88   8.176%   $212.9769   $212.98   $213.00   $213.00  
  Purchase #2 $141.45   11.669%   $157.9558   $157.96   $157.95   $158.00  
  Purchase #3 $33.48   8.384%   $36.287   $36.29   $36.30   $36.30  
  Purchase #4 $169.25   5.687%   $178.8752   $178.88   $178.90   $178.90  
  Purchase #5 $250.97   8.737%   $272.8972   $272.90   $272.90   $272.90  
  Purchase #6 $157.69   4.388%   $164.6094   $164.61   $164.60   $164.60  
  Purchase #7 $153.45   11.134%   $170.5351   $170.54   $170.55   $170.50  
  7 purchase totals = $1,103.17       $1,194.1366   $1,194.16   $1,194.20   $1,194.20