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	$130.62	10.631%	$144.5062	$144.51	$144.50	$144.50
Purchase #2	$242.51	5.223%	$255.1763	$255.18	$255.20	$255.20
Purchase #3	$204.35	13.861%	$232.675	$232.68	$232.70	$232.70
Purchase #4	$18.31	13.171%	$20.7216	$20.72	$20.70	$20.70
Purchase #5	$68.95	3.602%	$71.4336	$71.43	$71.45	$71.40
Purchase #6	$181.38	12.471%	$203.9999	$204.00	$204.00	$204.00
Purchase #7	$135.29	13.758%	$153.9032	$153.90	$153.90	$153.90
7 purchase totals =	$981.41		$1,082.4158	$1,082.42	$1,082.45	$1,082.40