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	$206.83	8.592%	$224.6008	$224.60	$224.60	$224.60
Purchase #2	$228.68	5.779%	$241.8954	$241.90	$241.90	$241.90
Purchase #3	$188.57	10.341%	$208.07	$208.07	$208.05	$208.10
Purchase #4	$205.43	8.495%	$222.8813	$222.88	$222.90	$222.90
Purchase #5	$58.32	3.302%	$60.2457	$60.25	$60.25	$60.20
Purchase #6	$9.78	4.740%	$10.2436	$10.24	$10.25	$10.20
Purchase #7	$66.94	9.808%	$73.5055	$73.51	$73.50	$73.50
7 purchase totals =	$964.55		$1,041.4423	$1,041.45	$1,041.45	$1,041.40