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	$87.27	6.533%	$92.9713	$92.97	$92.95	$93.00
Purchase #2	$159.37	9.548%	$174.5866	$174.59	$174.60	$174.60
Purchase #3	$166.50	4.395%	$173.8177	$173.82	$173.80	$173.80
Purchase #4	$242.56	13.245%	$274.6871	$274.69	$274.70	$274.70
Purchase #5	$225.55	13.136%	$255.1782	$255.18	$255.20	$255.20
Purchase #6	$150.42	9.731%	$165.0574	$165.06	$165.05	$165.10
Purchase #7	$160.83	5.594%	$169.8268	$169.83	$169.85	$169.80
7 purchase totals =	$1,192.50		$1,306.1251	$1,306.14	$1,306.15	$1,306.20