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	$39.92	11.584%	$44.5443	$44.54	$44.55	$44.50
Purchase #2	$86.85	6.409%	$92.4162	$92.42	$92.40	$92.40
Purchase #3	$88.32	5.121%	$92.8429	$92.84	$92.85	$92.80
Purchase #4	$132.91	13.653%	$151.0562	$151.06	$151.05	$151.10
Purchase #5	$86.37	3.631%	$89.5061	$89.51	$89.50	$89.50
Purchase #6	$229.77	3.408%	$237.6006	$237.60	$237.60	$237.60
Purchase #7	$176.72	6.343%	$187.9293	$187.93	$187.95	$187.90
7 purchase totals =	$840.86		$895.8956	$895.90	$895.90	$895.80