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	$182.40	4.851%	$191.2482	$191.25	$191.25	$191.20
Purchase #2	$115.72	5.240%	$121.7837	$121.78	$121.80	$121.80
Purchase #3	$219.59	4.114%	$228.6239	$228.62	$228.60	$228.60
Purchase #4	$165.94	9.509%	$181.7192	$181.72	$181.70	$181.70
Purchase #5	$137.43	3.776%	$142.6194	$142.62	$142.60	$142.60
Purchase #6	$27.51	10.659%	$30.4423	$30.44	$30.45	$30.40
Purchase #7	$102.64	6.525%	$109.3373	$109.34	$109.35	$109.30
7 purchase totals =	$951.23		$1,005.7740	$1,005.77	$1,005.75	$1,005.60