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	$188.78	11.648%	$210.7691	$210.77	$210.75	$210.80
Purchase #2	$33.56	4.598%	$35.1031	$35.10	$35.10	$35.10
Purchase #3	$225.37	3.707%	$233.7245	$233.72	$233.70	$233.70
Purchase #4	$10.70	13.801%	$12.1767	$12.18	$12.20	$12.20
Purchase #5	$54.90	12.598%	$61.8163	$61.82	$61.80	$61.80
Purchase #6	$187.25	3.823%	$194.4086	$194.41	$194.40	$194.40
Purchase #7	$31.54	9.464%	$34.5249	$34.52	$34.50	$34.50
7 purchase totals =	$732.10		$782.5232	$782.52	$782.45	$782.50