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	$244.68	5.816%	$258.9106	$258.91	$258.90	$258.90
Purchase #2	$44.35	5.718%	$46.8859	$46.89	$46.90	$46.90
Purchase #3	$199.72	11.116%	$221.9209	$221.92	$221.90	$221.90
Purchase #4	$215.77	9.280%	$235.7935	$235.79	$235.80	$235.80
Purchase #5	$34.86	12.721%	$39.2945	$39.29	$39.30	$39.30
Purchase #6	$149.85	11.798%	$167.5293	$167.53	$167.55	$167.50
Purchase #7	$135.69	4.195%	$141.3822	$141.38	$141.40	$141.40
7 purchase totals =	$1,024.92		$1,111.7169	$1,111.71	$1,111.75	$1,111.70