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	$217.35	9.323%	$237.6135	$237.61	$237.60	$237.60
Purchase #2	$230.93	12.256%	$259.2328	$259.23	$259.25	$259.20
Purchase #3	$39.42	10.278%	$43.4716	$43.47	$43.45	$43.50
Purchase #4	$147.46	3.366%	$152.4235	$152.42	$152.40	$152.40
Purchase #5	$19.98	10.713%	$22.1205	$22.12	$22.10	$22.10
Purchase #6	$126.36	8.470%	$137.0627	$137.06	$137.05	$137.10
Purchase #7	$196.50	13.260%	$222.5559	$222.56	$222.55	$222.60
7 purchase totals =	$978.00		$1,074.4805	$1,074.47	$1,074.40	$1,074.50