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	$45.52	8.298%	$49.2972	$49.30	$49.30	$49.30
Purchase #2	$107.46	12.821%	$121.2374	$121.24	$121.25	$121.20
Purchase #3	$30.86	3.150%	$31.8321	$31.83	$31.85	$31.80
Purchase #4	$95.40	10.581%	$105.4943	$105.49	$105.50	$105.50
Purchase #5	$30.73	13.410%	$34.8509	$34.85	$34.85	$34.90
Purchase #6	$17.47	5.422%	$18.4172	$18.42	$18.40	$18.40
Purchase #7	$80.75	5.605%	$85.276	$85.28	$85.30	$85.30
7 purchase totals =	$408.19		$446.4051	$446.41	$446.45	$446.40