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	$69.67	12.847%	$78.6205	$78.62	$78.60	$78.60
Purchase #2	$142.41	12.316%	$159.9492	$159.95	$159.95	$159.90
Purchase #3	$13.40	6.353%	$14.2513	$14.25	$14.25	$14.30
Purchase #4	$103.78	10.843%	$115.0329	$115.03	$115.05	$115.00
Purchase #5	$70.32	13.640%	$79.9116	$79.91	$79.90	$79.90
Purchase #6	$216.94	4.240%	$226.1383	$226.14	$226.15	$226.10
Purchase #7	$79.88	13.563%	$90.7141	$90.71	$90.70	$90.70
7 purchase totals =	$696.40		$764.6179	$764.61	$764.60	$764.50