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	$44.26	12.180%	$49.6509	$49.65	$49.65	$49.70
Purchase #2	$118.78	11.645%	$132.6119	$132.61	$132.60	$132.60
Purchase #3	$193.74	6.188%	$205.7286	$205.73	$205.75	$205.70
Purchase #4	$216.48	11.598%	$241.5874	$241.59	$241.60	$241.60
Purchase #5	$89.46	11.436%	$99.6906	$99.69	$99.70	$99.70
Purchase #6	$238.96	7.116%	$255.9644	$255.96	$255.95	$256.00
Purchase #7	$30.41	13.399%	$34.4846	$34.48	$34.50	$34.50
7 purchase totals =	$932.09		$1,019.7184	$1,019.71	$1,019.75	$1,019.80