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	$114.52	12.840%	$129.2244	$129.22	$129.20	$129.20
Purchase #2	$160.37	7.592%	$172.5453	$172.55	$172.55	$172.50
Purchase #3	$79.30	4.217%	$82.6441	$82.64	$82.65	$82.60
Purchase #4	$143.41	10.486%	$158.448	$158.45	$158.45	$158.40
Purchase #5	$70.40	13.230%	$79.7139	$79.71	$79.70	$79.70
Purchase #6	$215.35	10.231%	$237.3825	$237.38	$237.40	$237.40
Purchase #7	$146.88	10.674%	$162.558	$162.56	$162.55	$162.60
7 purchase totals =	$930.23		$1,022.5162	$1,022.51	$1,022.50	$1,022.40