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	$174.96	3.782%	$181.577	$181.58	$181.60	$181.60
Purchase #2	$26.55	8.363%	$28.7704	$28.77	$28.75	$28.80
Purchase #3	$27.55	5.848%	$29.1611	$29.16	$29.15	$29.20
Purchase #4	$138.30	10.283%	$152.5214	$152.52	$152.50	$152.50
Purchase #5	$74.29	5.286%	$78.217	$78.22	$78.20	$78.20
Purchase #6	$128.55	7.282%	$137.911	$137.91	$137.90	$137.90
Purchase #7	$38.65	7.616%	$41.5936	$41.59	$41.60	$41.60
7 purchase totals =	$608.85		$649.7515	$649.75	$649.70	$649.80