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	$168.25	10.262%	$185.5158	$185.52	$185.50	$185.50
Purchase #2	$73.27	12.686%	$82.565	$82.57	$82.55	$82.60
Purchase #3	$137.54	5.647%	$145.3069	$145.31	$145.30	$145.30
Purchase #4	$122.95	4.526%	$128.5147	$128.51	$128.50	$128.50
Purchase #5	$236.54	10.467%	$261.2986	$261.30	$261.30	$261.30
Purchase #6	$189.60	5.193%	$199.4459	$199.45	$199.45	$199.40
Purchase #7	$126.28	6.419%	$134.3859	$134.39	$134.40	$134.40
7 purchase totals =	$1,054.43		$1,137.0328	$1,137.05	$1,137.00	$1,137.00