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	$113.70	3.348%	$117.5067	$117.51	$117.50	$117.50
Purchase #2	$71.93	4.786%	$75.3726	$75.37	$75.35	$75.40
Purchase #3	$217.40	6.672%	$231.9049	$231.90	$231.90	$231.90
Purchase #4	$234.41	13.168%	$265.2771	$265.28	$265.30	$265.30
Purchase #5	$101.48	10.191%	$111.8218	$111.82	$111.80	$111.80
Purchase #6	$230.59	12.113%	$258.5214	$258.52	$258.50	$258.50
Purchase #7	$122.51	9.748%	$134.4523	$134.45	$134.45	$134.50
7 purchase totals =	$1,092.02		$1,194.8568	$1,194.85	$1,194.80	$1,194.90