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	$154.32	12.574%	$173.7242	$173.72	$173.70	$173.70
Purchase #2	$205.56	12.526%	$231.3084	$231.31	$231.30	$231.30
Purchase #3	$97.87	7.141%	$104.8589	$104.86	$104.85	$104.90
Purchase #4	$35.93	6.848%	$38.3905	$38.39	$38.40	$38.40
Purchase #5	$78.86	13.253%	$89.3113	$89.31	$89.30	$89.30
Purchase #6	$127.43	12.698%	$143.6111	$143.61	$143.60	$143.60
Purchase #7	$224.54	4.670%	$235.026	$235.03	$235.05	$235.00
7 purchase totals =	$924.51		$1,016.2304	$1,016.23	$1,016.20	$1,016.20