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	$228.71	7.606%	$246.1057	$246.11	$246.10	$246.10
Purchase #2	$104.79	13.670%	$119.1148	$119.11	$119.10	$119.10
Purchase #3	$171.42	11.567%	$191.2482	$191.25	$191.25	$191.20
Purchase #4	$130.46	8.160%	$141.1055	$141.11	$141.10	$141.10
Purchase #5	$112.59	13.366%	$127.6388	$127.64	$127.65	$127.60
Purchase #6	$241.43	10.807%	$267.5213	$267.52	$267.50	$267.50
Purchase #7	$49.27	9.773%	$54.0852	$54.09	$54.10	$54.10
7 purchase totals =	$1,038.67		$1,146.8195	$1,146.83	$1,146.80	$1,146.70