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	$40.78	11.671%	$45.5394	$45.54	$45.55	$45.50
Purchase #2	$171.48	13.388%	$194.4377	$194.44	$194.45	$194.40
Purchase #3	$76.75	4.467%	$80.1784	$80.18	$80.20	$80.20
Purchase #4	$86.51	6.709%	$92.314	$92.31	$92.30	$92.30
Purchase #5	$223.30	13.312%	$253.0257	$253.03	$253.05	$253.00
Purchase #6	$15.29	6.419%	$16.2715	$16.27	$16.25	$16.30
Purchase #7	$53.49	5.212%	$56.2779	$56.28	$56.30	$56.30
7 purchase totals =	$667.60		$738.0446	$738.05	$738.10	$738.00