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	$64.76	4.463%	$67.6502	$67.65	$67.65	$67.70
Purchase #2	$131.54	7.538%	$141.4555	$141.46	$141.45	$141.50
Purchase #3	$19.44	4.542%	$20.323	$20.32	$20.30	$20.30
Purchase #4	$82.81	6.375%	$88.0891	$88.09	$88.10	$88.10
Purchase #5	$207.41	13.406%	$235.2154	$235.22	$235.20	$235.20
Purchase #6	$159.52	3.304%	$164.7905	$164.79	$164.80	$164.80
Purchase #7	$11.54	5.162%	$12.1357	$12.14	$12.15	$12.10
7 purchase totals =	$677.02		$729.6594	$729.67	$729.65	$729.70