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	$156.45	9.712%	$171.6444	$171.64	$171.65	$171.60
Purchase #2	$84.38	8.211%	$91.3084	$91.31	$91.30	$91.30
Purchase #3	$150.43	9.563%	$164.8156	$164.82	$164.80	$164.80
Purchase #4	$61.90	6.338%	$65.8232	$65.82	$65.80	$65.80
Purchase #5	$217.84	3.313%	$225.057	$225.06	$225.05	$225.10
Purchase #6	$153.51	12.723%	$173.0411	$173.04	$173.05	$173.00
Purchase #7	$48.74	3.828%	$50.6058	$50.61	$50.60	$50.60
7 purchase totals =	$873.25		$942.2955	$942.30	$942.25	$942.20