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 $86.67   11.471%   $96.6119   $96.61   $96.60   $96.60  
  Purchase #2 $132.95   5.864%   $140.7462   $140.75   $140.75   $140.70  
  Purchase #3 $32.57   10.542%   $36.0035   $36.00   $36.00   $36.00  
  Purchase #4 $69.38   6.871%   $74.1471   $74.15   $74.15   $74.10  
  Purchase #5 $38.83   11.251%   $43.1988   $43.20   $43.20   $43.20  
  Purchase #6 $79.27   13.210%   $89.7416   $89.74   $89.75   $89.70  
  Purchase #7 $222.39   6.697%   $237.2835   $237.28   $237.30   $237.30  
  7 purchase totals = $662.06       $717.7326   $717.73   $717.75   $717.60