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	$109.29	9.123%	$119.2605	$119.26	$119.25	$119.30
Purchase #2	$180.75	3.768%	$187.5607	$187.56	$187.55	$187.60
Purchase #3	$37.42	13.857%	$42.6053	$42.61	$42.60	$42.60
Purchase #4	$230.78	12.408%	$259.4152	$259.42	$259.40	$259.40
Purchase #5	$168.58	11.205%	$187.4694	$187.47	$187.45	$187.50
Purchase #6	$163.31	7.487%	$175.537	$175.54	$175.55	$175.50
Purchase #7	$153.66	3.620%	$159.2225	$159.22	$159.20	$159.20
7 purchase totals =	$1,043.79		$1,131.0706	$1,131.08	$1,131.00	$1,131.10