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	$177.86	4.224%	$185.3728	$185.37	$185.35	$185.40
Purchase #2	$139.78	8.800%	$152.0806	$152.08	$152.10	$152.10
Purchase #3	$69.87	9.326%	$76.3861	$76.39	$76.40	$76.40
Purchase #4	$20.75	9.388%	$22.698	$22.70	$22.70	$22.70
Purchase #5	$103.65	5.277%	$109.1196	$109.12	$109.10	$109.10
Purchase #6	$250.68	13.314%	$284.0555	$284.06	$284.05	$284.10
Purchase #7	$39.87	7.538%	$42.8754	$42.88	$42.90	$42.90
7 purchase totals =	$802.46		$872.5880	$872.60	$872.60	$872.70