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	$24.76	3.430%	$25.6093	$25.61	$25.60	$25.60
Purchase #2	$67.90	9.722%	$74.5012	$74.50	$74.50	$74.50
Purchase #3	$176.74	11.212%	$196.5561	$196.56	$196.55	$196.60
Purchase #4	$245.73	4.522%	$256.8419	$256.84	$256.85	$256.80
Purchase #5	$158.71	11.773%	$177.3949	$177.39	$177.40	$177.40
Purchase #6	$140.74	9.322%	$153.8598	$153.86	$153.85	$153.90
Purchase #7	$72.46	13.284%	$82.0856	$82.09	$82.10	$82.10
7 purchase totals =	$887.04		$966.8488	$966.85	$966.85	$966.90