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	$164.49	10.324%	$181.4719	$181.47	$181.45	$181.50
Purchase #2	$146.45	3.811%	$152.0312	$152.03	$152.05	$152.00
Purchase #3	$127.38	4.854%	$133.563	$133.56	$133.55	$133.60
Purchase #4	$132.78	9.418%	$145.2852	$145.29	$145.30	$145.30
Purchase #5	$86.68	13.423%	$98.3151	$98.32	$98.30	$98.30
Purchase #6	$88.72	3.588%	$91.9033	$91.90	$91.90	$91.90
Purchase #7	$21.92	7.569%	$23.5791	$23.58	$23.60	$23.60
7 purchase totals =	$768.42		$826.1488	$826.15	$826.15	$826.20