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	$43.27	11.510%	$48.2504	$48.25	$48.25	$48.30
Purchase #2	$174.94	8.769%	$190.2805	$190.28	$190.30	$190.30
Purchase #3	$128.63	12.424%	$144.611	$144.61	$144.60	$144.60
Purchase #4	$55.91	11.837%	$62.5281	$62.53	$62.55	$62.50
Purchase #5	$168.60	9.852%	$185.2105	$185.21	$185.20	$185.20
Purchase #6	$146.64	8.866%	$159.6411	$159.64	$159.65	$159.60
Purchase #7	$176.94	9.248%	$193.3034	$193.30	$193.30	$193.30
7 purchase totals =	$894.93		$983.8250	$983.82	$983.85	$983.80