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	$178.65	3.723%	$185.3011	$185.30	$185.30	$185.30
Purchase #2	$192.32	10.233%	$212.0001	$212.00	$212.00	$212.00
Purchase #3	$235.38	8.302%	$254.9212	$254.92	$254.90	$254.90
Purchase #4	$72.44	13.717%	$82.3766	$82.38	$82.40	$82.40
Purchase #5	$59.53	12.342%	$66.8772	$66.88	$66.90	$66.90
Purchase #6	$111.99	5.638%	$118.304	$118.30	$118.30	$118.30
Purchase #7	$138.88	10.518%	$153.4874	$153.49	$153.50	$153.50
7 purchase totals =	$989.19		$1,073.2676	$1,073.27	$1,073.30	$1,073.30