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	$44.65	4.208%	$46.5289	$46.53	$46.55	$46.50
Purchase #2	$191.85	9.494%	$210.0642	$210.06	$210.05	$210.10
Purchase #3	$32.47	3.339%	$33.5542	$33.55	$33.55	$33.60
Purchase #4	$155.68	7.124%	$166.7706	$166.77	$166.75	$166.80
Purchase #5	$92.93	8.380%	$100.7175	$100.72	$100.70	$100.70
Purchase #6	$150.38	6.551%	$160.2314	$160.23	$160.25	$160.20
Purchase #7	$12.63	7.604%	$13.5904	$13.59	$13.60	$13.60
7 purchase totals =	$680.59		$731.4572	$731.45	$731.45	$731.50