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 $92.68   4.655%   $96.9943   $96.99   $97.00   $97.00  
  Purchase #2 $205.39   3.802%   $213.1989   $213.20   $213.20   $213.20  
  Purchase #3 $11.96   5.297%   $12.5935   $12.59   $12.60   $12.60  
  Purchase #4 $197.39   5.630%   $208.5031   $208.50   $208.50   $208.50  
  Purchase #5 $239.94   13.228%   $271.6793   $271.68   $271.70   $271.70  
  Purchase #6 $49.62   13.572%   $56.3544   $56.35   $56.35   $56.40  
  Purchase #7 $197.81   9.655%   $216.9086   $216.91   $216.90   $216.90  
  7 purchase totals = $994.79       $1,076.2321   $1,076.22   $1,076.25   $1,076.30