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	$126.29	13.708%	$143.6018	$143.60	$143.60	$143.60
Purchase #2	$151.30	10.192%	$166.7205	$166.72	$166.70	$166.70
Purchase #3	$39.41	5.171%	$41.4479	$41.45	$41.45	$41.40
Purchase #4	$83.73	4.117%	$87.1772	$87.18	$87.20	$87.20
Purchase #5	$156.81	13.619%	$178.166	$178.17	$178.15	$178.20
Purchase #6	$40.78	6.363%	$43.3748	$43.37	$43.35	$43.40
Purchase #7	$62.70	7.610%	$67.4715	$67.47	$67.45	$67.50
7 purchase totals =	$661.02		$727.9597	$727.96	$727.90	$728.00