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	$26.41	4.867%	$27.6954	$27.70	$27.70	$27.70
Purchase #2	$41.59	3.618%	$43.0947	$43.09	$43.10	$43.10
Purchase #3	$223.59	4.483%	$233.6135	$233.61	$233.60	$233.60
Purchase #4	$11.65	3.309%	$12.0355	$12.04	$12.05	$12.00
Purchase #5	$86.32	12.242%	$96.8873	$96.89	$96.90	$96.90
Purchase #6	$68.38	13.367%	$77.5204	$77.52	$77.50	$77.50
Purchase #7	$217.73	13.640%	$247.4284	$247.43	$247.45	$247.40
7 purchase totals =	$675.67		$738.2752	$738.28	$738.30	$738.20