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	$201.86	13.326%	$228.7599	$228.76	$228.75	$228.80
Purchase #2	$237.25	10.388%	$261.8955	$261.90	$261.90	$261.90
Purchase #3	$25.71	10.523%	$28.4155	$28.42	$28.40	$28.40
Purchase #4	$155.32	11.682%	$173.4645	$173.46	$173.45	$173.50
Purchase #5	$165.58	7.602%	$178.1674	$178.17	$178.15	$178.20
Purchase #6	$151.65	11.299%	$168.7849	$168.78	$168.80	$168.80
Purchase #7	$43.36	5.361%	$45.6845	$45.68	$45.70	$45.70
7 purchase totals =	$980.73		$1,085.1722	$1,085.17	$1,085.15	$1,085.30