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	$13.78	3.435%	$14.2533	$14.25	$14.25	$14.30
Purchase #2	$56.41	9.526%	$61.7836	$61.78	$61.80	$61.80
Purchase #3	$223.52	6.664%	$238.4154	$238.42	$238.40	$238.40
Purchase #4	$51.74	13.428%	$58.6876	$58.69	$58.70	$58.70
Purchase #5	$143.59	12.195%	$161.1008	$161.10	$161.10	$161.10
Purchase #6	$211.34	5.313%	$222.5685	$222.57	$222.55	$222.60
Purchase #7	$10.58	13.474%	$12.0055	$12.01	$12.00	$12.00
7 purchase totals =	$710.96		$768.8147	$768.82	$768.80	$768.90