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	$76.32	9.364%	$83.4666	$83.47	$83.45	$83.50
Purchase #2	$137.84	3.242%	$142.3088	$142.31	$142.30	$142.30
Purchase #3	$154.68	12.191%	$173.537	$173.54	$173.55	$173.50
Purchase #4	$101.88	9.824%	$111.8887	$111.89	$111.90	$111.90
Purchase #5	$151.84	9.398%	$166.1099	$166.11	$166.10	$166.10
Purchase #6	$127.41	8.554%	$138.3087	$138.31	$138.30	$138.30
Purchase #7	$222.78	4.388%	$232.5556	$232.56	$232.55	$232.60
7 purchase totals =	$972.75		$1,048.1753	$1,048.19	$1,048.15	$1,048.20