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 $180.58   8.528%   $195.9799   $195.98   $196.00   $196.00  
  Purchase #2 $46.90   9.845%   $51.5173   $51.52   $51.50   $51.50  
  Purchase #3 $148.48   10.707%   $164.3778   $164.38   $164.40   $164.40  
  Purchase #4 $248.71   4.145%   $259.019   $259.02   $259.00   $259.00  
  Purchase #5 $114.64   8.581%   $124.4773   $124.48   $124.50   $124.50  
  Purchase #6 $136.45   8.355%   $147.8504   $147.85   $147.85   $147.90  
  Purchase #7 $177.79   12.659%   $200.2964   $200.30   $200.30   $200.30  
  7 purchase totals = $1,053.55       $1,143.5181   $1,143.53   $1,143.55   $1,143.60