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	$226.28	12.587%	$254.7619	$254.76	$254.75	$254.80
Purchase #2	$228.53	12.412%	$256.8951	$256.90	$256.90	$256.90
Purchase #3	$184.45	12.854%	$208.1592	$208.16	$208.15	$208.20
Purchase #4	$11.83	5.844%	$12.5213	$12.52	$12.50	$12.50
Purchase #5	$94.76	10.106%	$104.3364	$104.34	$104.35	$104.30
Purchase #6	$186.30	6.786%	$198.9423	$198.94	$198.95	$198.90
Purchase #7	$71.82	8.475%	$77.9067	$77.91	$77.90	$77.90
7 purchase totals =	$1,003.97		$1,113.5229	$1,113.53	$1,113.50	$1,113.50