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	$90.80	13.502%	$103.0598	$103.06	$103.05	$103.10
Purchase #2	$92.32	11.783%	$103.1981	$103.20	$103.20	$103.20
Purchase #3	$69.91	11.694%	$78.0853	$78.09	$78.10	$78.10
Purchase #4	$130.43	9.643%	$143.0074	$143.01	$143.00	$143.00
Purchase #5	$46.94	7.804%	$50.6032	$50.60	$50.60	$50.60
Purchase #6	$55.77	12.277%	$62.6169	$62.62	$62.60	$62.60
Purchase #7	$169.46	13.396%	$192.1609	$192.16	$192.15	$192.20
7 purchase totals =	$655.63		$732.7316	$732.74	$732.70	$732.80