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	$54.78	9.804%	$60.1506	$60.15	$60.15	$60.20
Purchase #2	$221.27	13.429%	$250.9843	$250.98	$251.00	$251.00
Purchase #3	$244.68	12.139%	$274.3817	$274.38	$274.40	$274.40
Purchase #4	$81.28	11.537%	$90.6573	$90.66	$90.65	$90.70
Purchase #5	$56.47	5.481%	$59.5651	$59.57	$59.55	$59.60
Purchase #6	$174.90	5.622%	$184.7329	$184.73	$184.75	$184.70
Purchase #7	$127.73	12.429%	$143.6056	$143.61	$143.60	$143.60
7 purchase totals =	$961.11		$1,064.0775	$1,064.08	$1,064.10	$1,064.20