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	$231.34	11.799%	$258.6358	$258.64	$258.65	$258.60
Purchase #2	$97.92	7.749%	$105.5078	$105.51	$105.50	$105.50
Purchase #3	$152.43	5.153%	$160.2847	$160.28	$160.30	$160.30
Purchase #4	$181.76	6.672%	$193.887	$193.89	$193.90	$193.90
Purchase #5	$97.60	5.424%	$102.8938	$102.89	$102.90	$102.90
Purchase #6	$149.30	13.655%	$169.6869	$169.69	$169.70	$169.70
Purchase #7	$43.69	10.233%	$48.1608	$48.16	$48.15	$48.20
7 purchase totals =	$954.04		$1,039.0568	$1,039.06	$1,039.10	$1,039.10