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	$40.76	11.485%	$45.4413	$45.44	$45.45	$45.40
Purchase #2	$99.31	11.865%	$111.0931	$111.09	$111.10	$111.10
Purchase #3	$105.33	6.847%	$112.5419	$112.54	$112.55	$112.50
Purchase #4	$44.83	3.165%	$46.2489	$46.25	$46.25	$46.20
Purchase #5	$139.35	8.682%	$151.4484	$151.45	$151.45	$151.40
Purchase #6	$135.42	6.779%	$144.6001	$144.60	$144.60	$144.60
Purchase #7	$10.68	13.521%	$12.124	$12.12	$12.10	$12.10
7 purchase totals =	$575.68		$623.4977	$623.49	$623.50	$623.30