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	$158.64	8.661%	$172.3798	$172.38	$172.40	$172.40
Purchase #2	$130.55	9.134%	$142.4744	$142.47	$142.45	$142.50
Purchase #3	$43.49	9.664%	$47.6929	$47.69	$47.70	$47.70
Purchase #4	$187.28	9.737%	$205.5155	$205.52	$205.50	$205.50
Purchase #5	$128.37	6.333%	$136.4997	$136.50	$136.50	$136.50
Purchase #6	$126.31	5.654%	$133.4516	$133.45	$133.45	$133.50
Purchase #7	$119.58	4.325%	$124.7518	$124.75	$124.75	$124.80
7 purchase totals =	$894.22		$962.7657	$962.76	$962.75	$962.90