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	$32.92	13.483%	$37.3586	$37.36	$37.35	$37.40
Purchase #2	$62.70	5.343%	$66.0501	$66.05	$66.05	$66.10
Purchase #3	$17.49	7.544%	$18.8094	$18.81	$18.80	$18.80
Purchase #4	$96.77	7.173%	$103.7113	$103.71	$103.70	$103.70
Purchase #5	$36.50	6.393%	$38.8334	$38.83	$38.85	$38.80
Purchase #6	$10.71	6.778%	$11.4359	$11.44	$11.45	$11.40
Purchase #7	$18.48	7.426%	$19.8523	$19.85	$19.85	$19.90
7 purchase totals =	$275.57		$296.0510	$296.05	$296.05	$296.10