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	$214.38	4.125%	$223.2232	$223.22	$223.20	$223.20
Purchase #2	$144.99	12.347%	$162.8919	$162.89	$162.90	$162.90
Purchase #3	$28.58	11.577%	$31.8887	$31.89	$31.90	$31.90
Purchase #4	$141.62	11.843%	$158.3921	$158.39	$158.40	$158.40
Purchase #5	$163.90	12.780%	$184.8464	$184.85	$184.85	$184.80
Purchase #6	$11.29	11.369%	$12.5736	$12.57	$12.55	$12.60
Purchase #7	$54.30	13.593%	$61.681	$61.68	$61.70	$61.70
7 purchase totals =	$759.06		$835.4969	$835.49	$835.50	$835.50