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	$197.31	13.383%	$223.716	$223.72	$223.70	$223.70
Purchase #2	$140.41	9.557%	$153.829	$153.83	$153.85	$153.80
Purchase #3	$142.90	10.833%	$158.3804	$158.38	$158.40	$158.40
Purchase #4	$200.30	6.829%	$213.9785	$213.98	$214.00	$214.00
Purchase #5	$248.89	12.464%	$279.9116	$279.91	$279.90	$279.90
Purchase #6	$145.59	8.852%	$158.4776	$158.48	$158.50	$158.50
Purchase #7	$244.65	8.460%	$265.3474	$265.35	$265.35	$265.30
7 purchase totals =	$1,320.05		$1,453.6405	$1,453.65	$1,453.70	$1,453.60