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	$105.95	3.518%	$109.6773	$109.68	$109.70	$109.70
Purchase #2	$48.48	9.240%	$52.9596	$52.96	$52.95	$53.00
Purchase #3	$176.52	8.449%	$191.4342	$191.43	$191.45	$191.40
Purchase #4	$190.91	5.117%	$200.6789	$200.68	$200.70	$200.70
Purchase #5	$100.52	3.414%	$103.9518	$103.95	$103.95	$104.00
Purchase #6	$88.50	13.273%	$100.2466	$100.25	$100.25	$100.20
Purchase #7	$237.91	4.608%	$248.8729	$248.87	$248.85	$248.90
7 purchase totals =	$948.79		$1,007.8213	$1,007.82	$1,007.85	$1,007.90