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	$110.25	13.149%	$124.7468	$124.75	$124.75	$124.70
Purchase #2	$19.82	6.417%	$21.0918	$21.09	$21.10	$21.10
Purchase #3	$210.95	4.243%	$219.9006	$219.90	$219.90	$219.90
Purchase #4	$98.37	13.353%	$111.5053	$111.51	$111.50	$111.50
Purchase #5	$48.43	11.603%	$54.0493	$54.05	$54.05	$54.00
Purchase #6	$150.75	9.728%	$165.415	$165.42	$165.40	$165.40
Purchase #7	$54.33	5.660%	$57.4051	$57.41	$57.40	$57.40
7 purchase totals =	$692.90		$754.1139	$754.13	$754.10	$754.00