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	$183.28	8.705%	$199.2345	$199.23	$199.25	$199.20
Purchase #2	$160.69	9.819%	$176.4682	$176.47	$176.45	$176.50
Purchase #3	$81.76	10.718%	$90.523	$90.52	$90.50	$90.50
Purchase #4	$64.94	8.523%	$70.4748	$70.47	$70.45	$70.50
Purchase #5	$228.63	5.607%	$241.4493	$241.45	$241.45	$241.40
Purchase #6	$83.50	6.292%	$88.7538	$88.75	$88.75	$88.80
Purchase #7	$101.55	5.311%	$106.9433	$106.94	$106.95	$106.90
7 purchase totals =	$904.35		$973.8469	$973.83	$973.80	$973.80