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	$187.80	4.434%	$196.1271	$196.13	$196.15	$196.10
Purchase #2	$49.87	11.114%	$55.4126	$55.41	$55.40	$55.40
Purchase #3	$16.87	5.163%	$17.741	$17.74	$17.75	$17.70
Purchase #4	$42.93	8.179%	$46.4412	$46.44	$46.45	$46.40
Purchase #5	$172.83	4.253%	$180.1805	$180.18	$180.20	$180.20
Purchase #6	$116.49	13.752%	$132.5097	$132.51	$132.50	$132.50
Purchase #7	$10.37	7.851%	$11.1841	$11.18	$11.20	$11.20
7 purchase totals =	$597.16		$639.5962	$639.59	$639.65	$639.50