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	$221.74	9.388%	$242.557	$242.56	$242.55	$242.60
Purchase #2	$105.35	5.804%	$111.4645	$111.46	$111.45	$111.50
Purchase #3	$34.56	6.261%	$36.7238	$36.72	$36.70	$36.70
Purchase #4	$105.83	9.789%	$116.1897	$116.19	$116.20	$116.20
Purchase #5	$130.69	10.702%	$144.6764	$144.68	$144.70	$144.70
Purchase #6	$152.93	8.294%	$165.614	$165.61	$165.60	$165.60
Purchase #7	$95.43	10.424%	$105.3776	$105.38	$105.40	$105.40
7 purchase totals =	$846.53		$922.6030	$922.60	$922.60	$922.70