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	$53.67	10.251%	$59.1717	$59.17	$59.15	$59.20
Purchase #2	$50.93	6.176%	$54.0754	$54.08	$54.10	$54.10
Purchase #3	$133.67	12.422%	$150.2745	$150.27	$150.25	$150.30
Purchase #4	$161.46	13.364%	$183.0375	$183.04	$183.05	$183.00
Purchase #5	$34.50	3.293%	$35.6361	$35.64	$35.65	$35.60
Purchase #6	$249.73	5.211%	$262.7434	$262.74	$262.75	$262.70
Purchase #7	$235.41	12.411%	$264.6267	$264.63	$264.65	$264.60
7 purchase totals =	$919.37		$1,009.5653	$1,009.57	$1,009.60	$1,009.50