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	$191.91	10.547%	$212.1507	$212.15	$212.15	$212.20
Purchase #2	$52.60	13.506%	$59.7042	$59.70	$59.70	$59.70
Purchase #3	$142.40	11.164%	$158.2975	$158.30	$158.30	$158.30
Purchase #4	$95.45	4.842%	$100.0717	$100.07	$100.05	$100.10
Purchase #5	$106.54	13.520%	$120.9442	$120.94	$120.95	$120.90
Purchase #6	$82.28	3.871%	$85.4651	$85.47	$85.45	$85.50
Purchase #7	$198.26	8.209%	$214.5352	$214.54	$214.55	$214.50
7 purchase totals =	$869.44		$951.1686	$951.17	$951.15	$951.20