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 $114.44   7.150%   $122.6225   $122.62   $122.60   $122.60  
  Purchase #2 $202.51   7.305%   $217.3034   $217.30   $217.30   $217.30  
  Purchase #3 $230.59   3.635%   $238.9719   $238.97   $238.95   $239.00  
  Purchase #4 $116.86   4.849%   $122.5265   $122.53   $122.55   $122.50  
  Purchase #5 $37.62   13.102%   $42.549   $42.55   $42.55   $42.50  
  Purchase #6 $136.25   4.788%   $142.7737   $142.77   $142.75   $142.80  
  Purchase #7 $166.70   5.713%   $176.2236   $176.22   $176.20   $176.20  
  7 purchase totals = $1,004.97       $1,062.9706   $1,062.96   $1,062.90   $1,062.90