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	$229.34	3.583%	$237.5573	$237.56	$237.55	$237.60
Purchase #2	$134.39	7.853%	$144.9436	$144.94	$144.95	$144.90
Purchase #3	$71.87	6.256%	$76.3662	$76.37	$76.35	$76.40
Purchase #4	$65.94	6.586%	$70.2828	$70.28	$70.30	$70.30
Purchase #5	$83.91	6.246%	$89.151	$89.15	$89.15	$89.20
Purchase #6	$230.90	10.721%	$255.6548	$255.65	$255.65	$255.70
Purchase #7	$47.74	12.418%	$53.6684	$53.67	$53.65	$53.70
7 purchase totals =	$864.09		$927.6241	$927.62	$927.60	$927.80