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	$206.87	7.322%	$222.017	$222.02	$222.00	$222.00
Purchase #2	$36.41	10.699%	$40.3055	$40.31	$40.30	$40.30
Purchase #3	$45.94	4.658%	$48.0799	$48.08	$48.10	$48.10
Purchase #4	$240.79	5.784%	$254.7173	$254.72	$254.70	$254.70
Purchase #5	$171.35	9.351%	$187.3729	$187.37	$187.35	$187.40
Purchase #6	$23.59	3.565%	$24.431	$24.43	$24.45	$24.40
Purchase #7	$128.87	6.429%	$137.1551	$137.16	$137.15	$137.20
7 purchase totals =	$853.82		$914.0787	$914.09	$914.05	$914.10