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	$29.83	9.590%	$32.6907	$32.69	$32.70	$32.70
Purchase #2	$12.33	12.291%	$13.8455	$13.85	$13.85	$13.80
Purchase #3	$138.32	12.661%	$155.8327	$155.83	$155.85	$155.80
Purchase #4	$119.70	11.198%	$133.104	$133.10	$133.10	$133.10
Purchase #5	$151.60	9.594%	$166.1445	$166.14	$166.15	$166.10
Purchase #6	$178.82	12.255%	$200.7344	$200.73	$200.75	$200.70
Purchase #7	$92.54	13.687%	$105.2059	$105.21	$105.20	$105.20
7 purchase totals =	$723.14		$807.5577	$807.55	$807.60	$807.40