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	$9.29	10.441%	$10.26	$10.26	$10.25	$10.30
Purchase #2	$138.29	9.597%	$151.5617	$151.56	$151.55	$151.60
Purchase #3	$188.51	4.193%	$196.4142	$196.41	$196.40	$196.40
Purchase #4	$249.51	10.671%	$276.1352	$276.14	$276.15	$276.10
Purchase #5	$241.44	8.181%	$261.1922	$261.19	$261.20	$261.20
Purchase #6	$120.70	9.309%	$131.936	$131.94	$131.95	$131.90
Purchase #7	$85.78	3.288%	$88.6004	$88.60	$88.60	$88.60
7 purchase totals =	$1,033.52		$1,116.0997	$1,116.10	$1,116.10	$1,116.10