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	$133.46	11.203%	$148.4115	$148.41	$148.40	$148.40
Purchase #2	$195.53	5.259%	$205.8129	$205.81	$205.80	$205.80
Purchase #3	$237.60	3.253%	$245.3291	$245.33	$245.35	$245.30
Purchase #4	$94.97	6.424%	$101.0709	$101.07	$101.05	$101.10
Purchase #5	$61.30	8.745%	$66.6607	$66.66	$66.65	$66.70
Purchase #6	$103.77	7.591%	$111.6472	$111.65	$111.65	$111.60
Purchase #7	$11.89	5.284%	$12.5183	$12.52	$12.50	$12.50
7 purchase totals =	$838.52		$891.4506	$891.45	$891.40	$891.40