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	$73.60	6.784%	$78.593	$78.59	$78.60	$78.60
Purchase #2	$153.94	4.589%	$161.0043	$161.00	$161.00	$161.00
Purchase #3	$58.52	9.583%	$64.128	$64.13	$64.15	$64.10
Purchase #4	$130.70	5.507%	$137.8976	$137.90	$137.90	$137.90
Purchase #5	$88.34	4.806%	$92.5856	$92.59	$92.60	$92.60
Purchase #6	$145.47	4.227%	$151.619	$151.62	$151.60	$151.60
Purchase #7	$57.70	6.396%	$61.3905	$61.39	$61.40	$61.40
7 purchase totals =	$708.27		$747.2180	$747.22	$747.25	$747.20