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	$43.25	12.259%	$48.552	$48.55	$48.55	$48.60
Purchase #2	$225.32	4.672%	$235.847	$235.85	$235.85	$235.80
Purchase #3	$10.68	12.483%	$12.0132	$12.01	$12.00	$12.00
Purchase #4	$30.32	10.851%	$33.61	$33.61	$33.60	$33.60
Purchase #5	$136.47	10.782%	$151.1842	$151.18	$151.20	$151.20
Purchase #6	$51.76	6.532%	$55.141	$55.14	$55.15	$55.10
Purchase #7	$22.60	7.288%	$24.2471	$24.25	$24.25	$24.20
7 purchase totals =	$520.40		$560.5945	$560.59	$560.60	$560.50