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	$46.68	12.609%	$52.5659	$52.57	$52.55	$52.60
Purchase #2	$246.25	13.221%	$278.8067	$278.81	$278.80	$278.80
Purchase #3	$223.36	5.479%	$235.5979	$235.60	$235.60	$235.60
Purchase #4	$43.94	3.694%	$45.5631	$45.56	$45.55	$45.60
Purchase #5	$78.50	5.784%	$83.0404	$83.04	$83.05	$83.00
Purchase #6	$134.64	8.153%	$145.6172	$145.62	$145.60	$145.60
Purchase #7	$167.37	6.782%	$178.721	$178.72	$178.70	$178.70
7 purchase totals =	$940.74		$1,019.9122	$1,019.92	$1,019.85	$1,019.90