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	$173.56	4.228%	$180.8981	$180.90	$180.90	$180.90
Purchase #2	$152.29	9.394%	$166.5961	$166.60	$166.60	$166.60
Purchase #3	$244.79	4.831%	$256.6158	$256.62	$256.60	$256.60
Purchase #4	$58.54	9.195%	$63.9228	$63.92	$63.90	$63.90
Purchase #5	$175.87	8.380%	$190.6079	$190.61	$190.60	$190.60
Purchase #6	$247.28	3.380%	$255.6381	$255.64	$255.65	$255.60
Purchase #7	$62.28	7.611%	$67.0201	$67.02	$67.00	$67.00
7 purchase totals =	$1,114.61		$1,181.2989	$1,181.31	$1,181.25	$1,181.20