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	$10.30	3.122%	$10.6216	$10.62	$10.60	$10.60
Purchase #2	$216.69	7.738%	$233.4575	$233.46	$233.45	$233.50
Purchase #3	$207.27	6.390%	$220.5146	$220.51	$220.50	$220.50
Purchase #4	$188.27	10.806%	$208.6145	$208.61	$208.60	$208.60
Purchase #5	$237.69	12.864%	$268.2664	$268.27	$268.25	$268.30
Purchase #6	$21.77	12.790%	$24.5544	$24.55	$24.55	$24.60
Purchase #7	$142.26	7.247%	$152.5696	$152.57	$152.55	$152.60
7 purchase totals =	$1,024.25		$1,118.5986	$1,118.59	$1,118.50	$1,118.70