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	$145.47	11.794%	$162.6267	$162.63	$162.65	$162.60
Purchase #2	$99.47	5.574%	$105.0145	$105.01	$105.00	$105.00
Purchase #3	$249.99	13.793%	$284.4711	$284.47	$284.45	$284.50
Purchase #4	$88.86	13.414%	$100.7797	$100.78	$100.80	$100.80
Purchase #5	$23.85	7.854%	$25.7232	$25.72	$25.70	$25.70
Purchase #6	$38.53	10.346%	$42.5163	$42.52	$42.50	$42.50
Purchase #7	$15.28	5.541%	$16.1267	$16.13	$16.15	$16.10
7 purchase totals =	$661.45		$737.2582	$737.26	$737.25	$737.20