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	$164.60	4.848%	$172.5798	$172.58	$172.60	$172.60
Purchase #2	$174.91	3.782%	$181.5251	$181.53	$181.55	$181.50
Purchase #3	$152.52	10.575%	$168.649	$168.65	$168.65	$168.60
Purchase #4	$30.45	8.214%	$32.9512	$32.95	$32.95	$33.00
Purchase #5	$240.82	3.505%	$249.2607	$249.26	$249.25	$249.30
Purchase #6	$111.43	9.248%	$121.735	$121.74	$121.75	$121.70
Purchase #7	$77.98	10.379%	$86.0735	$86.07	$86.05	$86.10
7 purchase totals =	$952.71		$1,012.7743	$1,012.78	$1,012.80	$1,012.80