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 $61.26   7.663%   $65.9544   $65.95   $65.95   $66.00  
  Purchase #2 $72.63   9.470%   $79.5081   $79.51   $79.50   $79.50  
  Purchase #3 $152.27   6.559%   $162.2574   $162.26   $162.25   $162.30  
  Purchase #4 $242.59   8.650%   $263.574   $263.57   $263.55   $263.60  
  Purchase #5 $219.42   9.355%   $239.9467   $239.95   $239.95   $239.90  
  Purchase #6 $82.85   4.163%   $86.299   $86.30   $86.30   $86.30  
  Purchase #7 $138.61   6.347%   $147.4076   $147.41   $147.40   $147.40  
  7 purchase totals = $969.63       $1,044.9472   $1,044.95   $1,044.90   $1,045.00