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	$149.83	8.127%	$162.0067	$162.01	$162.00	$162.00
Purchase #2	$240.70	3.146%	$248.2724	$248.27	$248.25	$248.30
Purchase #3	$158.92	5.760%	$168.0738	$168.07	$168.05	$168.10
Purchase #4	$240.39	8.637%	$261.1525	$261.15	$261.15	$261.20
Purchase #5	$123.29	13.289%	$139.674	$139.67	$139.65	$139.70
Purchase #6	$18.75	5.844%	$19.8458	$19.85	$19.85	$19.80
Purchase #7	$169.52	9.619%	$185.8261	$185.83	$185.85	$185.80
7 purchase totals =	$1,101.40		$1,184.8513	$1,184.85	$1,184.80	$1,184.90