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	$140.26	9.798%	$154.0027	$154.00	$154.00	$154.00
Purchase #2	$58.50	13.785%	$66.5642	$66.56	$66.55	$66.60
Purchase #3	$204.28	13.487%	$231.8312	$231.83	$231.85	$231.80
Purchase #4	$54.55	5.356%	$57.4717	$57.47	$57.45	$57.50
Purchase #5	$38.52	9.396%	$42.1393	$42.14	$42.15	$42.10
Purchase #6	$72.95	13.138%	$82.5342	$82.53	$82.55	$82.50
Purchase #7	$157.30	10.452%	$173.741	$173.74	$173.75	$173.70
7 purchase totals =	$726.36		$808.2843	$808.27	$808.30	$808.20