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	$175.55	10.157%	$193.3806	$193.38	$193.40	$193.40
Purchase #2	$38.67	9.235%	$42.2412	$42.24	$42.25	$42.20
Purchase #3	$52.55	4.310%	$54.8149	$54.81	$54.80	$54.80
Purchase #4	$216.38	12.795%	$244.0658	$244.07	$244.05	$244.10
Purchase #5	$121.80	13.837%	$138.6535	$138.65	$138.65	$138.70
Purchase #6	$183.30	7.391%	$196.8477	$196.85	$196.85	$196.80
Purchase #7	$131.75	10.222%	$145.2175	$145.22	$145.20	$145.20
7 purchase totals =	$920.00		$1,015.2212	$1,015.22	$1,015.20	$1,015.20