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	$193.72	8.708%	$210.5891	$210.59	$210.60	$210.60
Purchase #2	$97.91	13.767%	$111.3893	$111.39	$111.40	$111.40
Purchase #3	$59.70	4.703%	$62.5077	$62.51	$62.50	$62.50
Purchase #4	$142.62	11.424%	$158.9129	$158.91	$158.90	$158.90
Purchase #5	$228.39	5.574%	$241.1205	$241.12	$241.10	$241.10
Purchase #6	$75.52	9.519%	$82.7087	$82.71	$82.70	$82.70
Purchase #7	$133.41	7.256%	$143.0902	$143.09	$143.10	$143.10
7 purchase totals =	$931.27		$1,010.3184	$1,010.32	$1,010.30	$1,010.30