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	$170.94	4.683%	$178.9451	$178.95	$178.95	$178.90
Purchase #2	$101.55	8.262%	$109.9401	$109.94	$109.95	$109.90
Purchase #3	$135.76	11.414%	$151.2556	$151.26	$151.25	$151.30
Purchase #4	$128.29	13.391%	$145.4693	$145.47	$145.45	$145.50
Purchase #5	$13.93	3.779%	$14.4564	$14.46	$14.45	$14.50
Purchase #6	$111.52	5.437%	$117.5833	$117.58	$117.60	$117.60
Purchase #7	$89.68	3.556%	$92.869	$92.87	$92.85	$92.90
7 purchase totals =	$751.67		$810.5188	$810.53	$810.50	$810.60