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	$138.56	9.603%	$151.8659	$151.87	$151.85	$151.90
Purchase #2	$53.36	13.186%	$60.396	$60.40	$60.40	$60.40
Purchase #3	$152.72	8.595%	$165.8463	$165.85	$165.85	$165.80
Purchase #4	$238.78	8.170%	$258.2883	$258.29	$258.30	$258.30
Purchase #5	$172.27	10.526%	$190.4031	$190.40	$190.40	$190.40
Purchase #6	$31.95	4.446%	$33.3705	$33.37	$33.35	$33.40
Purchase #7	$127.54	13.338%	$144.5513	$144.55	$144.55	$144.60
7 purchase totals =	$915.18		$1,004.7214	$1,004.73	$1,004.70	$1,004.80