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	$176.30	4.607%	$184.4221	$184.42	$184.40	$184.40
Purchase #2	$102.77	13.730%	$116.8803	$116.88	$116.90	$116.90
Purchase #3	$231.41	11.725%	$258.5428	$258.54	$258.55	$258.50
Purchase #4	$130.33	5.293%	$137.2284	$137.23	$137.25	$137.20
Purchase #5	$13.29	10.608%	$14.6998	$14.70	$14.70	$14.70
Purchase #6	$95.38	8.342%	$103.3366	$103.34	$103.35	$103.30
Purchase #7	$197.68	3.555%	$204.7075	$204.71	$204.70	$204.70
7 purchase totals =	$947.16		$1,019.8175	$1,019.82	$1,019.85	$1,019.70