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	$95.75	7.843%	$103.2597	$103.26	$103.25	$103.30
Purchase #2	$234.89	9.633%	$257.517	$257.52	$257.50	$257.50
Purchase #3	$188.61	4.143%	$196.4241	$196.42	$196.40	$196.40
Purchase #4	$49.97	4.515%	$52.2261	$52.23	$52.25	$52.20
Purchase #5	$138.26	8.552%	$150.084	$150.08	$150.10	$150.10
Purchase #6	$199.33	10.104%	$219.4703	$219.47	$219.45	$219.50
Purchase #7	$217.39	10.339%	$239.866	$239.87	$239.85	$239.90
7 purchase totals =	$1,124.20		$1,218.8472	$1,218.85	$1,218.80	$1,218.90