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	$80.43	8.369%	$87.1612	$87.16	$87.15	$87.20
Purchase #2	$153.47	3.278%	$158.5007	$158.50	$158.50	$158.50
Purchase #3	$78.66	12.445%	$88.4492	$88.45	$88.45	$88.40
Purchase #4	$10.87	6.684%	$11.5966	$11.60	$11.60	$11.60
Purchase #5	$134.42	7.712%	$144.7865	$144.79	$144.80	$144.80
Purchase #6	$127.82	11.483%	$142.4976	$142.50	$142.50	$142.50
Purchase #7	$133.73	8.829%	$145.537	$145.54	$145.55	$145.50
7 purchase totals =	$719.40		$778.5288	$778.54	$778.55	$778.50