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	$103.89	8.236%	$112.4464	$112.45	$112.45	$112.40
Purchase #2	$150.26	9.637%	$164.7406	$164.74	$164.75	$164.70
Purchase #3	$243.85	7.663%	$262.5362	$262.54	$262.55	$262.50
Purchase #4	$107.39	3.671%	$111.3323	$111.33	$111.35	$111.30
Purchase #5	$214.93	8.426%	$233.04	$233.04	$233.05	$233.00
Purchase #6	$10.25	5.166%	$10.7795	$10.78	$10.80	$10.80
Purchase #7	$121.81	8.638%	$132.3319	$132.33	$132.35	$132.30
7 purchase totals =	$952.38		$1,027.2069	$1,027.21	$1,027.30	$1,027.00