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	$116.32	9.803%	$127.7228	$127.72	$127.70	$127.70
Purchase #2	$147.66	3.650%	$153.0496	$153.05	$153.05	$153.00
Purchase #3	$147.40	7.399%	$158.3061	$158.31	$158.30	$158.30
Purchase #4	$74.45	6.555%	$79.3302	$79.33	$79.35	$79.30
Purchase #5	$132.92	7.235%	$142.5368	$142.54	$142.55	$142.50
Purchase #6	$229.30	6.180%	$243.4707	$243.47	$243.45	$243.50
Purchase #7	$155.96	6.832%	$166.6152	$166.62	$166.60	$166.60
7 purchase totals =	$1,004.01		$1,071.0314	$1,071.04	$1,071.00	$1,070.90