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	$221.90	3.393%	$229.4291	$229.43	$229.45	$229.40
Purchase #2	$55.47	10.628%	$61.3654	$61.37	$61.35	$61.40
Purchase #3	$159.28	5.838%	$168.5788	$168.58	$168.60	$168.60
Purchase #4	$216.65	6.196%	$230.0736	$230.07	$230.05	$230.10
Purchase #5	$82.86	7.688%	$89.2303	$89.23	$89.25	$89.20
Purchase #6	$86.93	5.715%	$91.898	$91.90	$91.90	$91.90
Purchase #7	$50.89	4.262%	$53.0589	$53.06	$53.05	$53.10
7 purchase totals =	$873.98		$923.6341	$923.64	$923.65	$923.70