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	$178.42	7.232%	$191.3233	$191.32	$191.30	$191.30
Purchase #2	$74.49	6.309%	$79.1896	$79.19	$79.20	$79.20
Purchase #3	$183.95	9.229%	$200.9267	$200.93	$200.95	$200.90
Purchase #4	$139.61	6.383%	$148.5213	$148.52	$148.50	$148.50
Purchase #5	$52.57	13.819%	$59.8346	$59.83	$59.85	$59.80
Purchase #6	$53.28	10.649%	$58.9538	$58.95	$58.95	$59.00
Purchase #7	$14.91	3.765%	$15.4714	$15.47	$15.45	$15.50
7 purchase totals =	$697.23		$754.2207	$754.21	$754.20	$754.20