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	$159.94	8.478%	$173.4997	$173.50	$173.50	$173.50
Purchase #2	$137.78	4.724%	$144.2887	$144.29	$144.30	$144.30
Purchase #3	$47.81	3.573%	$49.5183	$49.52	$49.50	$49.50
Purchase #4	$102.56	8.313%	$111.0858	$111.09	$111.10	$111.10
Purchase #5	$101.58	8.613%	$110.3291	$110.33	$110.35	$110.30
Purchase #6	$222.36	11.289%	$247.4622	$247.46	$247.45	$247.50
Purchase #7	$173.27	7.373%	$186.0452	$186.05	$186.05	$186.00
7 purchase totals =	$945.30		$1,022.2290	$1,022.24	$1,022.25	$1,022.20