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	$178.91	11.248%	$199.0338	$199.03	$199.05	$199.00
Purchase #2	$158.70	3.662%	$164.5116	$164.51	$164.50	$164.50
Purchase #3	$52.43	13.595%	$59.5579	$59.56	$59.55	$59.60
Purchase #4	$95.46	8.446%	$103.5226	$103.52	$103.50	$103.50
Purchase #5	$173.52	7.544%	$186.6103	$186.61	$186.60	$186.60
Purchase #6	$111.59	4.267%	$116.3515	$116.35	$116.35	$116.40
Purchase #7	$63.34	12.781%	$71.4355	$71.44	$71.45	$71.40
7 purchase totals =	$833.95		$901.0232	$901.02	$901.00	$901.00