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	$200.86	10.698%	$222.348	$222.35	$222.35	$222.30
Purchase #2	$241.94	5.456%	$255.1402	$255.14	$255.15	$255.10
Purchase #3	$199.25	12.776%	$224.7062	$224.71	$224.70	$224.70
Purchase #4	$180.34	7.639%	$194.1162	$194.12	$194.10	$194.10
Purchase #5	$29.95	8.245%	$32.4194	$32.42	$32.40	$32.40
Purchase #6	$93.27	13.282%	$105.6581	$105.66	$105.65	$105.70
Purchase #7	$128.61	11.718%	$143.6805	$143.68	$143.70	$143.70
7 purchase totals =	$1,074.22		$1,178.0686	$1,178.08	$1,178.05	$1,178.00