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	$86.96	3.613%	$90.1019	$90.10	$90.10	$90.10
Purchase #2	$212.55	4.308%	$221.7067	$221.71	$221.70	$221.70
Purchase #3	$52.54	13.785%	$59.7826	$59.78	$59.80	$59.80
Purchase #4	$172.45	12.298%	$193.6579	$193.66	$193.65	$193.70
Purchase #5	$249.84	5.822%	$264.3857	$264.39	$264.40	$264.40
Purchase #6	$16.64	6.686%	$17.7526	$17.75	$17.75	$17.80
Purchase #7	$171.95	9.676%	$188.5879	$188.59	$188.60	$188.60
7 purchase totals =	$962.93		$1,035.9753	$1,035.98	$1,036.00	$1,036.10