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	$118.58	7.217%	$127.1379	$127.14	$127.15	$127.10
Purchase #2	$234.75	13.795%	$267.1338	$267.13	$267.15	$267.10
Purchase #3	$199.81	10.676%	$221.1417	$221.14	$221.15	$221.10
Purchase #4	$121.60	13.139%	$137.577	$137.58	$137.60	$137.60
Purchase #5	$71.78	9.123%	$78.3285	$78.33	$78.35	$78.30
Purchase #6	$56.69	4.226%	$59.0857	$59.09	$59.10	$59.10
Purchase #7	$138.89	3.165%	$143.2859	$143.29	$143.30	$143.30
7 purchase totals =	$942.10		$1,033.6905	$1,033.70	$1,033.80	$1,033.60