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	$148.31	3.466%	$153.4504	$153.45	$153.45	$153.50
Purchase #2	$161.76	8.340%	$175.2508	$175.25	$175.25	$175.30
Purchase #3	$167.66	4.845%	$175.7831	$175.78	$175.80	$175.80
Purchase #4	$57.48	4.488%	$60.0597	$60.06	$60.05	$60.10
Purchase #5	$59.53	4.868%	$62.4279	$62.43	$62.45	$62.40
Purchase #6	$52.37	13.753%	$59.5724	$59.57	$59.55	$59.60
Purchase #7	$42.65	5.622%	$45.0478	$45.05	$45.05	$45.00
7 purchase totals =	$689.76		$731.5921	$731.59	$731.60	$731.70