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	$78.70	13.383%	$89.2324	$89.23	$89.25	$89.20
Purchase #2	$12.80	11.375%	$14.256	$14.26	$14.25	$14.30
Purchase #3	$60.59	7.509%	$65.1397	$65.14	$65.15	$65.10
Purchase #4	$151.85	6.746%	$162.0938	$162.09	$162.10	$162.10
Purchase #5	$57.32	12.599%	$64.5417	$64.54	$64.55	$64.50
Purchase #6	$67.26	8.568%	$73.0228	$73.02	$73.00	$73.00
Purchase #7	$139.89	11.734%	$156.3047	$156.30	$156.30	$156.30
7 purchase totals =	$568.41		$624.5911	$624.58	$624.60	$624.50