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	$223.56	6.294%	$237.6309	$237.63	$237.65	$237.60
Purchase #2	$122.52	4.309%	$127.7994	$127.80	$127.80	$127.80
Purchase #3	$117.34	4.827%	$123.004	$123.00	$123.00	$123.00
Purchase #4	$35.48	5.544%	$37.447	$37.45	$37.45	$37.40
Purchase #5	$127.90	9.435%	$139.9674	$139.97	$139.95	$140.00
Purchase #6	$191.40	7.271%	$205.3167	$205.32	$205.30	$205.30
Purchase #7	$128.65	11.622%	$143.6017	$143.60	$143.60	$143.60
7 purchase totals =	$946.85		$1,014.7671	$1,014.77	$1,014.75	$1,014.70