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	$13.31	9.409%	$14.5623	$14.56	$14.55	$14.60
Purchase #2	$22.54	10.261%	$24.8528	$24.85	$24.85	$24.90
Purchase #3	$84.32	8.734%	$91.6845	$91.68	$91.70	$91.70
Purchase #4	$249.46	11.599%	$278.3949	$278.39	$278.40	$278.40
Purchase #5	$250.69	7.255%	$268.8776	$268.88	$268.90	$268.90
Purchase #6	$215.38	10.518%	$238.0337	$238.03	$238.05	$238.00
Purchase #7	$80.25	13.316%	$90.9361	$90.94	$90.95	$90.90
7 purchase totals =	$915.95		$1,007.3419	$1,007.33	$1,007.40	$1,007.40