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	$94.47	11.520%	$105.3529	$105.35	$105.35	$105.40
Purchase #2	$51.70	5.560%	$54.5745	$54.57	$54.55	$54.60
Purchase #3	$11.70	13.525%	$13.2824	$13.28	$13.30	$13.30
Purchase #4	$153.66	12.491%	$172.8537	$172.85	$172.85	$172.90
Purchase #5	$212.84	3.816%	$220.962	$220.96	$220.95	$221.00
Purchase #6	$88.34	12.480%	$99.3648	$99.36	$99.35	$99.40
Purchase #7	$92.51	12.792%	$104.3439	$104.34	$104.35	$104.30
7 purchase totals =	$705.22		$770.7342	$770.71	$770.70	$770.90