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	$77.86	13.748%	$88.5642	$88.56	$88.55	$88.60
Purchase #2	$223.70	4.343%	$233.4153	$233.42	$233.40	$233.40
Purchase #3	$55.79	11.662%	$62.2962	$62.30	$62.30	$62.30
Purchase #4	$111.67	10.603%	$123.5104	$123.51	$123.50	$123.50
Purchase #5	$123.73	5.113%	$130.0563	$130.06	$130.05	$130.10
Purchase #6	$88.62	8.810%	$96.4274	$96.43	$96.45	$96.40
Purchase #7	$120.36	5.601%	$127.1014	$127.10	$127.10	$127.10
7 purchase totals =	$801.73		$861.3712	$861.38	$861.35	$861.40