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	$68.70	5.382%	$72.3974	$72.40	$72.40	$72.40
Purchase #2	$236.61	10.849%	$262.2798	$262.28	$262.30	$262.30
Purchase #3	$139.25	13.577%	$158.156	$158.16	$158.15	$158.20
Purchase #4	$123.62	5.491%	$130.408	$130.41	$130.40	$130.40
Purchase #5	$101.90	9.645%	$111.7283	$111.73	$111.75	$111.70
Purchase #6	$143.91	13.433%	$163.2414	$163.24	$163.25	$163.20
Purchase #7	$164.31	12.135%	$184.249	$184.25	$184.25	$184.20
7 purchase totals =	$978.30		$1,082.4599	$1,082.47	$1,082.50	$1,082.40