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	$49.27	11.712%	$55.0405	$55.04	$55.05	$55.00
Purchase #2	$198.83	9.703%	$218.1225	$218.12	$218.10	$218.10
Purchase #3	$22.81	13.204%	$25.8218	$25.82	$25.80	$25.80
Purchase #4	$98.56	12.867%	$111.2417	$111.24	$111.25	$111.20
Purchase #5	$223.65	7.783%	$241.0567	$241.06	$241.05	$241.10
Purchase #6	$223.43	10.372%	$246.6042	$246.60	$246.60	$246.60
Purchase #7	$153.66	11.864%	$171.8902	$171.89	$171.90	$171.90
7 purchase totals =	$970.21		$1,069.7776	$1,069.77	$1,069.75	$1,069.70