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	$33.93	4.329%	$35.3988	$35.40	$35.40	$35.40
Purchase #2	$53.52	4.728%	$56.0504	$56.05	$56.05	$56.10
Purchase #3	$99.37	11.746%	$111.042	$111.04	$111.05	$111.00
Purchase #4	$196.55	13.150%	$222.3963	$222.40	$222.40	$222.40
Purchase #5	$242.80	4.164%	$252.9102	$252.91	$252.90	$252.90
Purchase #6	$32.71	11.457%	$36.4576	$36.46	$36.45	$36.50
Purchase #7	$105.39	3.248%	$108.8131	$108.81	$108.80	$108.80
7 purchase totals =	$764.27		$823.0684	$823.07	$823.05	$823.10