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	$229.89	10.833%	$254.794	$254.79	$254.80	$254.80
Purchase #2	$59.93	10.229%	$66.0602	$66.06	$66.05	$66.10
Purchase #3	$200.43	10.669%	$221.8139	$221.81	$221.80	$221.80
Purchase #4	$71.39	4.467%	$74.579	$74.58	$74.60	$74.60
Purchase #5	$37.57	7.267%	$40.3002	$40.30	$40.30	$40.30
Purchase #6	$183.76	4.393%	$191.8326	$191.83	$191.85	$191.80
Purchase #7	$203.57	10.326%	$224.5906	$224.59	$224.60	$224.60
7 purchase totals =	$986.54		$1,073.9705	$1,073.96	$1,074.00	$1,074.00