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	$24.66	13.738%	$28.0478	$28.05	$28.05	$28.00
Purchase #2	$160.41	13.171%	$181.5376	$181.54	$181.55	$181.50
Purchase #3	$18.92	13.195%	$21.4165	$21.42	$21.40	$21.40
Purchase #4	$136.67	11.548%	$152.4527	$152.45	$152.45	$152.50
Purchase #5	$246.71	13.447%	$279.8851	$279.89	$279.90	$279.90
Purchase #6	$204.49	5.368%	$215.467	$215.47	$215.45	$215.50
Purchase #7	$120.71	10.145%	$132.956	$132.96	$132.95	$133.00
7 purchase totals =	$912.57		$1,011.7627	$1,011.78	$1,011.75	$1,011.80