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	$96.42	4.181%	$100.4513	$100.45	$100.45	$100.50
Purchase #2	$50.93	5.271%	$53.6145	$53.61	$53.60	$53.60
Purchase #3	$173.48	13.275%	$196.5095	$196.51	$196.50	$196.50
Purchase #4	$45.77	6.467%	$48.7299	$48.73	$48.75	$48.70
Purchase #5	$194.81	9.700%	$213.7066	$213.71	$213.70	$213.70
Purchase #6	$17.36	11.684%	$19.3883	$19.39	$19.40	$19.40
Purchase #7	$66.71	8.177%	$72.1649	$72.16	$72.15	$72.20
7 purchase totals =	$645.48		$704.5650	$704.56	$704.55	$704.60