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	$152.59	5.132%	$160.4209	$160.42	$160.40	$160.40
Purchase #2	$104.43	13.152%	$118.1646	$118.16	$118.15	$118.20
Purchase #3	$105.70	5.756%	$111.7841	$111.78	$111.80	$111.80
Purchase #4	$146.92	5.304%	$154.7126	$154.71	$154.70	$154.70
Purchase #5	$34.40	3.149%	$35.4833	$35.48	$35.50	$35.50
Purchase #6	$150.59	4.845%	$157.8861	$157.89	$157.90	$157.90
Purchase #7	$47.83	12.118%	$53.626	$53.63	$53.65	$53.60
7 purchase totals =	$742.46		$792.0776	$792.07	$792.10	$792.10