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 $22.93   13.568%   $26.0411   $26.04   $26.05   $26.00  
  Purchase #2 $180.69   9.141%   $197.2069   $197.21   $197.20   $197.20  
  Purchase #3 $172.40   12.865%   $194.5793   $194.58   $194.60   $194.60  
  Purchase #4 $177.68   8.285%   $192.4008   $192.40   $192.40   $192.40  
  Purchase #5 $122.28   4.261%   $127.4904   $127.49   $127.50   $127.50  
  Purchase #6 $235.99   3.426%   $244.075   $244.08   $244.10   $244.10  
  Purchase #7 $92.42   3.628%   $95.773   $95.77   $95.75   $95.80  
  7 purchase totals = $1,004.39       $1,077.5665   $1,077.57   $1,077.60   $1,077.60