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	$225.49	7.126%	$241.5584	$241.56	$241.55	$241.60
Purchase #2	$190.75	11.406%	$212.5069	$212.51	$212.50	$212.50
Purchase #3	$101.59	9.675%	$111.4188	$111.42	$111.40	$111.40
Purchase #4	$216.68	8.104%	$234.2397	$234.24	$234.25	$234.20
Purchase #5	$112.91	13.120%	$127.7238	$127.72	$127.70	$127.70
Purchase #6	$136.45	3.217%	$140.8396	$140.84	$140.85	$140.80
Purchase #7	$53.89	9.567%	$59.0457	$59.05	$59.05	$59.00
7 purchase totals =	$1,037.76		$1,127.3329	$1,127.34	$1,127.30	$1,127.20