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	$38.26	11.345%	$42.6006	$42.60	$42.60	$42.60
Purchase #2	$63.34	9.362%	$69.2699	$69.27	$69.25	$69.30
Purchase #3	$12.49	11.704%	$13.9518	$13.95	$13.95	$14.00
Purchase #4	$164.95	4.394%	$172.1979	$172.20	$172.20	$172.20
Purchase #5	$198.28	7.866%	$213.8767	$213.88	$213.90	$213.90
Purchase #6	$157.52	11.158%	$175.0961	$175.10	$175.10	$175.10
Purchase #7	$123.72	12.604%	$139.3137	$139.31	$139.30	$139.30
7 purchase totals =	$758.56		$826.3067	$826.31	$826.30	$826.40