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	$32.41	4.129%	$33.7482	$33.75	$33.75	$33.70
Purchase #2	$52.64	5.277%	$55.4178	$55.42	$55.40	$55.40
Purchase #3	$100.95	3.532%	$104.5156	$104.52	$104.50	$104.50
Purchase #4	$102.82	8.748%	$111.8147	$111.81	$111.80	$111.80
Purchase #5	$18.79	3.688%	$19.483	$19.48	$19.50	$19.50
Purchase #6	$126.57	5.729%	$133.8212	$133.82	$133.80	$133.80
Purchase #7	$14.64	11.271%	$16.2901	$16.29	$16.30	$16.30
7 purchase totals =	$448.82		$475.0906	$475.09	$475.05	$475.00