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	$134.56	11.485%	$150.0142	$150.01	$150.00	$150.00
Purchase #2	$9.66	6.713%	$10.3085	$10.31	$10.30	$10.30
Purchase #3	$107.71	6.237%	$114.4279	$114.43	$114.45	$114.40
Purchase #4	$89.29	13.838%	$101.646	$101.65	$101.65	$101.60
Purchase #5	$100.60	4.420%	$105.0465	$105.05	$105.05	$105.00
Purchase #6	$109.38	12.828%	$123.4113	$123.41	$123.40	$123.40
Purchase #7	$74.59	7.648%	$80.2946	$80.29	$80.30	$80.30
7 purchase totals =	$625.79		$685.1490	$685.15	$685.15	$685.00