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	$231.27	10.601%	$255.7869	$255.79	$255.80	$255.80
Purchase #2	$179.55	13.825%	$204.3728	$204.37	$204.35	$204.40
Purchase #3	$172.85	11.627%	$192.9473	$192.95	$192.95	$192.90
Purchase #4	$132.53	10.873%	$146.94	$146.94	$146.95	$146.90
Purchase #5	$223.51	4.288%	$233.0941	$233.09	$233.10	$233.10
Purchase #6	$50.62	11.380%	$56.3806	$56.38	$56.40	$56.40
Purchase #7	$198.72	5.236%	$209.125	$209.13	$209.15	$209.10
7 purchase totals =	$1,189.05		$1,298.6467	$1,298.65	$1,298.70	$1,298.60