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	$44.83	3.772%	$46.521	$46.52	$46.50	$46.50
Purchase #2	$182.68	5.455%	$192.6452	$192.65	$192.65	$192.60
Purchase #3	$113.32	13.565%	$128.6919	$128.69	$128.70	$128.70
Purchase #4	$132.53	10.743%	$146.7677	$146.77	$146.75	$146.80
Purchase #5	$37.46	5.159%	$39.3926	$39.39	$39.40	$39.40
Purchase #6	$143.72	5.729%	$151.9537	$151.95	$151.95	$152.00
Purchase #7	$194.63	7.549%	$209.3226	$209.32	$209.30	$209.30
7 purchase totals =	$849.17		$915.2947	$915.29	$915.25	$915.30