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	$209.28	11.336%	$233.004	$233.00	$233.00	$233.00
Purchase #2	$19.43	10.730%	$21.5148	$21.51	$21.50	$21.50
Purchase #3	$217.31	12.554%	$244.5911	$244.59	$244.60	$244.60
Purchase #4	$203.44	9.420%	$222.604	$222.60	$222.60	$222.60
Purchase #5	$230.87	3.311%	$238.5141	$238.51	$238.50	$238.50
Purchase #6	$5.83	11.783%	$6.5169	$6.52	$6.50	$6.50
Purchase #7	$8.44	12.352%	$9.4825	$9.48	$9.50	$9.50
7 purchase totals =	$894.60		$976.2274	$976.21	$976.20	$976.20