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	$143.35	7.611%	$154.2604	$154.26	$154.25	$154.30
Purchase #2	$30.25	8.519%	$32.827	$32.83	$32.85	$32.80
Purchase #3	$105.75	12.355%	$118.8154	$118.82	$118.80	$118.80
Purchase #4	$164.45	8.324%	$178.1388	$178.14	$178.15	$178.10
Purchase #5	$178.51	10.186%	$196.693	$196.69	$196.70	$196.70
Purchase #6	$24.89	9.417%	$27.2339	$27.23	$27.25	$27.20
Purchase #7	$12.79	8.801%	$13.9156	$13.92	$13.90	$13.90
7 purchase totals =	$659.99		$721.8841	$721.89	$721.90	$721.80