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	$49.35	9.698%	$54.136	$54.14	$54.15	$54.10
Purchase #2	$112.93	5.121%	$118.7131	$118.71	$118.70	$118.70
Purchase #3	$162.83	5.757%	$172.2041	$172.20	$172.20	$172.20
Purchase #4	$170.52	10.521%	$188.4604	$188.46	$188.45	$188.50
Purchase #5	$250.93	5.791%	$265.4614	$265.46	$265.45	$265.50
Purchase #6	$104.36	11.414%	$116.2717	$116.27	$116.25	$116.30
Purchase #7	$50.56	7.210%	$54.2054	$54.21	$54.20	$54.20
7 purchase totals =	$901.48		$969.4521	$969.45	$969.40	$969.50