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	$152.71	13.146%	$172.7853	$172.79	$172.80	$172.80
Purchase #2	$80.78	7.372%	$86.7351	$86.74	$86.75	$86.70
Purchase #3	$106.29	4.557%	$111.1336	$111.13	$111.15	$111.10
Purchase #4	$158.68	7.275%	$170.224	$170.22	$170.20	$170.20
Purchase #5	$241.89	11.177%	$268.926	$268.93	$268.95	$268.90
Purchase #6	$31.39	11.714%	$35.067	$35.07	$35.05	$35.10
Purchase #7	$128.66	3.693%	$133.4114	$133.41	$133.40	$133.40
7 purchase totals =	$900.40		$978.2824	$978.29	$978.30	$978.20