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	$61.71	8.445%	$66.9214	$66.92	$66.90	$66.90
Purchase #2	$94.32	13.346%	$106.9079	$106.91	$106.90	$106.90
Purchase #3	$26.83	3.381%	$27.7371	$27.74	$27.75	$27.70
Purchase #4	$219.57	8.608%	$238.4706	$238.47	$238.45	$238.50
Purchase #5	$97.70	13.779%	$111.1621	$111.16	$111.15	$111.20
Purchase #6	$86.79	6.131%	$92.1111	$92.11	$92.10	$92.10
Purchase #7	$152.31	4.364%	$158.9568	$158.96	$158.95	$159.00
7 purchase totals =	$739.23		$802.2670	$802.27	$802.20	$802.30