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	$175.56	7.206%	$188.2109	$188.21	$188.20	$188.20
Purchase #2	$81.82	12.192%	$91.7955	$91.80	$91.80	$91.80
Purchase #3	$237.74	7.458%	$255.4706	$255.47	$255.45	$255.50
Purchase #4	$146.28	6.374%	$155.6039	$155.60	$155.60	$155.60
Purchase #5	$125.56	3.353%	$129.77	$129.77	$129.75	$129.80
Purchase #6	$123.59	3.383%	$127.771	$127.77	$127.75	$127.80
Purchase #7	$228.92	10.211%	$252.295	$252.30	$252.30	$252.30
7 purchase totals =	$1,119.47		$1,200.9169	$1,200.92	$1,200.85	$1,201.00