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	$141.48	3.734%	$146.7629	$146.76	$146.75	$146.80
Purchase #2	$51.56	6.729%	$55.0295	$55.03	$55.05	$55.00
Purchase #3	$139.92	13.314%	$158.5489	$158.55	$158.55	$158.50
Purchase #4	$91.76	9.632%	$100.5983	$100.60	$100.60	$100.60
Purchase #5	$42.92	3.778%	$44.5415	$44.54	$44.55	$44.50
Purchase #6	$7.41	11.747%	$8.2805	$8.28	$8.30	$8.30
Purchase #7	$46.45	10.706%	$51.4229	$51.42	$51.40	$51.40
7 purchase totals =	$521.50		$565.1845	$565.18	$565.20	$565.10