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	$51.72	3.616%	$53.5902	$53.59	$53.60	$53.60
Purchase #2	$230.42	4.357%	$240.4594	$240.46	$240.45	$240.50
Purchase #3	$110.34	10.176%	$121.5682	$121.57	$121.55	$121.60
Purchase #4	$52.46	11.588%	$58.5391	$58.54	$58.55	$58.50
Purchase #5	$124.69	7.754%	$134.3585	$134.36	$134.35	$134.40
Purchase #6	$172.74	13.630%	$196.2845	$196.28	$196.30	$196.30
Purchase #7	$64.85	10.599%	$71.7235	$71.72	$71.70	$71.70
7 purchase totals =	$807.22		$876.5234	$876.52	$876.50	$876.60