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 $145.55   11.783%   $162.7002   $162.70   $162.70   $162.70  
  Purchase #2 $208.54   10.624%   $230.6953   $230.70   $230.70   $230.70  
  Purchase #3 $83.80   10.858%   $92.899   $92.90   $92.90   $92.90  
  Purchase #4 $81.88   13.424%   $92.8716   $92.87   $92.85   $92.90  
  Purchase #5 $239.60   7.211%   $256.8776   $256.88   $256.90   $256.90  
  Purchase #6 $201.35   4.594%   $210.6   $210.60   $210.60   $210.60  
  Purchase #7 $14.70   5.520%   $15.5114   $15.51   $15.50   $15.50  
  7 purchase totals = $975.42       $1,062.1551   $1,062.16   $1,062.15   $1,062.20