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	$149.61	8.672%	$162.5842	$162.58	$162.60	$162.60
Purchase #2	$112.77	9.763%	$123.7797	$123.78	$123.80	$123.80
Purchase #3	$145.53	12.815%	$164.1797	$164.18	$164.20	$164.20
Purchase #4	$56.93	13.490%	$64.6099	$64.61	$64.60	$64.60
Purchase #5	$163.75	5.355%	$172.5188	$172.52	$172.50	$172.50
Purchase #6	$180.28	4.843%	$189.011	$189.01	$189.00	$189.00
Purchase #7	$134.69	12.319%	$151.2825	$151.28	$151.30	$151.30
7 purchase totals =	$943.56		$1,027.9658	$1,027.96	$1,028.00	$1,028.00