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	$132.42	12.413%	$148.8573	$148.86	$148.85	$148.90
Purchase #2	$173.97	7.118%	$186.3532	$186.35	$186.35	$186.40
Purchase #3	$9.54	9.681%	$10.4636	$10.46	$10.45	$10.50
Purchase #4	$143.71	10.192%	$158.3569	$158.36	$158.35	$158.40
Purchase #5	$95.61	8.265%	$103.5122	$103.51	$103.50	$103.50
Purchase #6	$131.84	13.658%	$149.8467	$149.85	$149.85	$149.80
Purchase #7	$196.45	8.157%	$212.4744	$212.47	$212.45	$212.50
7 purchase totals =	$883.54		$969.8643	$969.86	$969.80	$970.00