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	$242.72	8.547%	$263.4653	$263.47	$263.45	$263.50
Purchase #2	$248.98	7.644%	$268.012	$268.01	$268.00	$268.00
Purchase #3	$247.69	3.181%	$255.569	$255.57	$255.55	$255.60
Purchase #4	$173.73	3.525%	$179.854	$179.85	$179.85	$179.90
Purchase #5	$12.66	3.494%	$13.1023	$13.10	$13.10	$13.10
Purchase #6	$47.55	11.753%	$53.1386	$53.14	$53.15	$53.10
Purchase #7	$9.81	4.463%	$10.2478	$10.25	$10.25	$10.20
7 purchase totals =	$983.14		$1,043.3890	$1,043.39	$1,043.35	$1,043.40