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	$176.55	4.339%	$184.2105	$184.21	$184.20	$184.20
Purchase #2	$159.32	12.246%	$178.8303	$178.83	$178.85	$178.80
Purchase #3	$53.39	6.559%	$56.8919	$56.89	$56.90	$56.90
Purchase #4	$129.60	11.150%	$144.0504	$144.05	$144.05	$144.10
Purchase #5	$135.42	5.255%	$142.5363	$142.54	$142.55	$142.50
Purchase #6	$159.27	6.281%	$169.2737	$169.27	$169.25	$169.30
Purchase #7	$16.91	11.244%	$18.8114	$18.81	$18.80	$18.80
7 purchase totals =	$830.46		$894.6045	$894.60	$894.60	$894.60