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	$191.47	7.289%	$205.4262	$205.43	$205.45	$205.40
Purchase #2	$60.42	8.154%	$65.3466	$65.35	$65.35	$65.30
Purchase #3	$132.74	8.276%	$143.7256	$143.73	$143.75	$143.70
Purchase #4	$149.59	7.748%	$161.1802	$161.18	$161.20	$161.20
Purchase #5	$128.40	11.732%	$143.4639	$143.46	$143.45	$143.50
Purchase #6	$246.84	6.379%	$262.5859	$262.59	$262.60	$262.60
Purchase #7	$81.75	9.591%	$89.5906	$89.59	$89.60	$89.60
7 purchase totals =	$991.21		$1,071.3190	$1,071.33	$1,071.40	$1,071.30