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 $61.45   5.690%   $64.9465   $64.95   $64.95   $64.90  
  Purchase #2 $12.45   12.769%   $14.0397   $14.04   $14.05   $14.00  
  Purchase #3 $175.95   9.102%   $191.965   $191.97   $191.95   $192.00  
  Purchase #4 $159.33   10.468%   $176.0087   $176.01   $176.00   $176.00  
  Purchase #5 $147.51   13.457%   $167.3604   $167.36   $167.35   $167.40  
  Purchase #6 $12.67   11.231%   $14.093   $14.09   $14.10   $14.10  
  Purchase #7 $197.59   8.571%   $214.5254   $214.53   $214.55   $214.50  
  7 purchase totals = $766.95       $842.9387   $842.95   $842.95   $842.90