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	$144.33	13.750%	$164.1754	$164.18	$164.20	$164.20
Purchase #2	$109.28	12.579%	$123.0263	$123.03	$123.05	$123.00
Purchase #3	$133.43	6.135%	$141.6159	$141.62	$141.60	$141.60
Purchase #4	$212.25	10.251%	$234.0077	$234.01	$234.00	$234.00
Purchase #5	$144.71	6.367%	$153.9237	$153.92	$153.90	$153.90
Purchase #6	$155.26	6.458%	$165.2867	$165.29	$165.30	$165.30
Purchase #7	$48.78	3.261%	$50.3707	$50.37	$50.35	$50.40
7 purchase totals =	$948.04		$1,032.4064	$1,032.42	$1,032.40	$1,032.40