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	$148.39	5.650%	$156.774	$156.77	$156.75	$156.80
Purchase #2	$83.28	9.631%	$91.3007	$91.30	$91.30	$91.30
Purchase #3	$242.38	8.268%	$262.42	$262.42	$262.40	$262.40
Purchase #4	$167.65	13.268%	$189.8938	$189.89	$189.90	$189.90
Purchase #5	$151.71	5.147%	$159.5185	$159.52	$159.50	$159.50
Purchase #6	$46.55	3.496%	$48.1774	$48.18	$48.20	$48.20
Purchase #7	$177.73	7.515%	$191.0864	$191.09	$191.10	$191.10
7 purchase totals =	$1,017.69		$1,099.1708	$1,099.17	$1,099.15	$1,099.20