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	$132.40	10.593%	$146.4251	$146.43	$146.45	$146.40
Purchase #2	$41.69	9.236%	$45.5405	$45.54	$45.55	$45.50
Purchase #3	$178.75	6.506%	$190.3795	$190.38	$190.40	$190.40
Purchase #4	$226.67	9.254%	$247.646	$247.65	$247.65	$247.60
Purchase #5	$177.49	12.199%	$199.142	$199.14	$199.15	$199.10
Purchase #6	$143.29	7.301%	$153.7516	$153.75	$153.75	$153.80
Purchase #7	$171.94	4.518%	$179.7082	$179.71	$179.70	$179.70
7 purchase totals =	$1,072.23		$1,162.5929	$1,162.60	$1,162.65	$1,162.50