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	$125.99	13.766%	$143.3338	$143.33	$143.35	$143.30
Purchase #2	$35.83	12.666%	$40.3682	$40.37	$40.35	$40.40
Purchase #3	$111.71	10.470%	$123.406	$123.41	$123.40	$123.40
Purchase #4	$151.62	5.254%	$159.5861	$159.59	$159.60	$159.60
Purchase #5	$162.43	7.125%	$174.0031	$174.00	$174.00	$174.00
Purchase #6	$247.93	7.823%	$267.3256	$267.33	$267.35	$267.30
Purchase #7	$172.65	9.595%	$189.2158	$189.22	$189.20	$189.20
7 purchase totals =	$1,008.16		$1,097.2386	$1,097.25	$1,097.25	$1,097.20