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	$80.88	6.243%	$85.9293	$85.93	$85.95	$85.90
Purchase #2	$215.48	6.429%	$229.3332	$229.33	$229.35	$229.30
Purchase #3	$41.93	4.819%	$43.9506	$43.95	$43.95	$44.00
Purchase #4	$105.25	5.823%	$111.3787	$111.38	$111.40	$111.40
Purchase #5	$60.75	5.418%	$64.0414	$64.04	$64.05	$64.00
Purchase #6	$223.90	10.491%	$247.3893	$247.39	$247.40	$247.40
Purchase #7	$16.49	8.321%	$17.8621	$17.86	$17.85	$17.90
7 purchase totals =	$744.68		$799.8846	$799.88	$799.95	$799.90