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	$47.28	12.695%	$53.2822	$53.28	$53.30	$53.30
Purchase #2	$30.29	5.748%	$32.0311	$32.03	$32.05	$32.00
Purchase #3	$40.99	6.749%	$43.7564	$43.76	$43.75	$43.80
Purchase #4	$92.47	7.675%	$99.5671	$99.57	$99.55	$99.60
Purchase #5	$61.76	6.473%	$65.7577	$65.76	$65.75	$65.80
Purchase #6	$40.68	12.530%	$45.7772	$45.78	$45.80	$45.80
Purchase #7	$103.31	3.830%	$107.2668	$107.27	$107.25	$107.30
7 purchase totals =	$416.78		$447.4385	$447.45	$447.45	$447.60