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	$24.62	4.605%	$25.7538	$25.75	$25.75	$25.80
Purchase #2	$32.98	5.290%	$34.7246	$34.72	$34.70	$34.70
Purchase #3	$62.93	5.287%	$66.2571	$66.26	$66.25	$66.30
Purchase #4	$153.74	7.678%	$165.5442	$165.54	$165.55	$165.50
Purchase #5	$142.25	6.487%	$151.4778	$151.48	$151.50	$151.50
Purchase #6	$74.40	10.632%	$82.3102	$82.31	$82.30	$82.30
Purchase #7	$140.58	12.859%	$158.6572	$158.66	$158.65	$158.70
7 purchase totals =	$631.50		$684.7249	$684.72	$684.70	$684.80