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	$114.64	10.153%	$126.2794	$126.28	$126.30	$126.30
Purchase #2	$73.85	6.321%	$78.5181	$78.52	$78.50	$78.50
Purchase #3	$236.45	9.312%	$258.4682	$258.47	$258.45	$258.50
Purchase #4	$157.31	13.370%	$178.3423	$178.34	$178.35	$178.30
Purchase #5	$20.61	7.401%	$22.1353	$22.14	$22.15	$22.10
Purchase #6	$42.65	13.630%	$48.4632	$48.46	$48.45	$48.50
Purchase #7	$51.54	11.347%	$57.3882	$57.39	$57.40	$57.40
7 purchase totals =	$697.05		$769.5947	$769.60	$769.60	$769.60