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	$103.94	5.145%	$109.2877	$109.29	$109.30	$109.30
Purchase #2	$178.51	3.477%	$184.7168	$184.72	$184.70	$184.70
Purchase #3	$197.62	7.805%	$213.0442	$213.04	$213.05	$213.00
Purchase #4	$189.61	11.335%	$211.1023	$211.10	$211.10	$211.10
Purchase #5	$48.68	12.824%	$54.9227	$54.92	$54.90	$54.90
Purchase #6	$163.85	13.129%	$185.3619	$185.36	$185.35	$185.40
Purchase #7	$104.45	6.434%	$111.1703	$111.17	$111.15	$111.20
7 purchase totals =	$986.66		$1,069.6059	$1,069.60	$1,069.55	$1,069.60