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	$168.73	4.609%	$176.5068	$176.51	$176.50	$176.50
Purchase #2	$97.43	6.819%	$104.0738	$104.07	$104.05	$104.10
Purchase #3	$79.28	7.483%	$85.2125	$85.21	$85.20	$85.20
Purchase #4	$43.42	12.427%	$48.8158	$48.82	$48.80	$48.80
Purchase #5	$111.48	13.748%	$126.8063	$126.81	$126.80	$126.80
Purchase #6	$34.91	11.391%	$38.8866	$38.89	$38.90	$38.90
Purchase #7	$151.45	7.219%	$162.3832	$162.38	$162.40	$162.40
7 purchase totals =	$686.70		$742.6850	$742.69	$742.65	$742.70