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	$83.43	12.761%	$94.0765	$94.08	$94.10	$94.10
Purchase #2	$38.82	10.717%	$42.9803	$42.98	$43.00	$43.00
Purchase #3	$207.57	3.439%	$214.7083	$214.71	$214.70	$214.70
Purchase #4	$98.27	13.395%	$111.4333	$111.43	$111.45	$111.40
Purchase #5	$18.98	11.741%	$21.2084	$21.21	$21.20	$21.20
Purchase #6	$65.92	6.119%	$69.9536	$69.95	$69.95	$70.00
Purchase #7	$65.62	10.819%	$72.7194	$72.72	$72.70	$72.70
7 purchase totals =	$578.61		$627.0798	$627.08	$627.10	$627.10