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	$45.94	5.739%	$48.5765	$48.58	$48.60	$48.60
Purchase #2	$183.86	8.750%	$199.9478	$199.95	$199.95	$199.90
Purchase #3	$221.77	11.466%	$247.1981	$247.20	$247.20	$247.20
Purchase #4	$237.81	11.388%	$264.8918	$264.89	$264.90	$264.90
Purchase #5	$244.28	8.556%	$265.1806	$265.18	$265.20	$265.20
Purchase #6	$51.90	13.792%	$59.058	$59.06	$59.05	$59.10
Purchase #7	$72.44	11.152%	$80.5185	$80.52	$80.50	$80.50
7 purchase totals =	$1,058.00		$1,165.3713	$1,165.38	$1,165.40	$1,165.40