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	$80.49	11.532%	$89.7721	$89.77	$89.75	$89.80
Purchase #2	$77.53	5.231%	$81.5856	$81.59	$81.60	$81.60
Purchase #3	$32.54	10.604%	$35.9905	$35.99	$36.00	$36.00
Purchase #4	$148.69	3.258%	$153.5343	$153.53	$153.55	$153.50
Purchase #5	$88.42	13.832%	$100.6503	$100.65	$100.65	$100.70
Purchase #6	$17.53	3.622%	$18.1649	$18.16	$18.15	$18.20
Purchase #7	$162.91	5.663%	$172.1356	$172.14	$172.15	$172.10
7 purchase totals =	$608.11		$651.8333	$651.83	$651.85	$651.90