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	$172.25	4.802%	$180.5214	$180.52	$180.50	$180.50
Purchase #2	$40.89	6.296%	$43.4644	$43.46	$43.45	$43.50
Purchase #3	$149.48	10.174%	$164.6881	$164.69	$164.70	$164.70
Purchase #4	$57.98	4.200%	$60.4152	$60.42	$60.40	$60.40
Purchase #5	$76.65	11.387%	$85.3781	$85.38	$85.40	$85.40
Purchase #6	$53.38	6.378%	$56.7846	$56.78	$56.80	$56.80
Purchase #7	$146.88	4.585%	$153.6144	$153.61	$153.60	$153.60
7 purchase totals =	$697.51		$744.8662	$744.86	$744.85	$744.90