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	$152.49	7.647%	$164.1509	$164.15	$164.15	$164.20
Purchase #2	$93.52	12.496%	$105.2063	$105.21	$105.20	$105.20
Purchase #3	$39.65	13.861%	$45.1459	$45.15	$45.15	$45.10
Purchase #4	$48.81	13.722%	$55.5077	$55.51	$55.50	$55.50
Purchase #5	$214.64	6.613%	$228.8341	$228.83	$228.85	$228.80
Purchase #6	$193.70	10.270%	$213.593	$213.59	$213.60	$213.60
Purchase #7	$39.34	3.233%	$40.6119	$40.61	$40.60	$40.60
7 purchase totals =	$782.15		$853.0498	$853.05	$853.05	$853.00