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	$224.31	13.449%	$254.4775	$254.48	$254.50	$254.50
Purchase #2	$51.91	3.271%	$53.608	$53.61	$53.60	$53.60
Purchase #3	$221.29	6.685%	$236.0832	$236.08	$236.10	$236.10
Purchase #4	$235.48	13.130%	$266.3985	$266.40	$266.40	$266.40
Purchase #5	$63.52	3.635%	$65.829	$65.83	$65.85	$65.80
Purchase #6	$114.48	11.491%	$127.6349	$127.63	$127.65	$127.60
Purchase #7	$49.39	8.395%	$53.5363	$53.54	$53.55	$53.50
7 purchase totals =	$960.38		$1,057.5674	$1,057.57	$1,057.65	$1,057.50