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	$184.89	3.561%	$191.4739	$191.47	$191.45	$191.50
Purchase #2	$244.94	13.393%	$277.7448	$277.74	$277.75	$277.70
Purchase #3	$165.25	8.140%	$178.7014	$178.70	$178.70	$178.70
Purchase #4	$175.59	5.111%	$184.5644	$184.56	$184.55	$184.60
Purchase #5	$69.45	4.795%	$72.7801	$72.78	$72.80	$72.80
Purchase #6	$52.54	11.551%	$58.6089	$58.61	$58.60	$58.60
Purchase #7	$240.71	8.846%	$262.0032	$262.00	$262.00	$262.00
7 purchase totals =	$1,133.37		$1,225.8767	$1,225.86	$1,225.85	$1,225.90