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	$210.87	10.630%	$233.2855	$233.29	$233.30	$233.30
Purchase #2	$172.75	13.760%	$196.5204	$196.52	$196.50	$196.50
Purchase #3	$100.99	4.247%	$105.279	$105.28	$105.30	$105.30
Purchase #4	$91.48	13.539%	$103.8655	$103.87	$103.85	$103.90
Purchase #5	$159.62	10.651%	$176.6211	$176.62	$176.60	$176.60
Purchase #6	$168.89	9.275%	$184.5545	$184.55	$184.55	$184.60
Purchase #7	$245.42	4.523%	$256.5203	$256.52	$256.50	$256.50
7 purchase totals =	$1,150.02		$1,256.6463	$1,256.65	$1,256.60	$1,256.70