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	$129.31	6.653%	$137.913	$137.91	$137.90	$137.90
Purchase #2	$93.67	7.403%	$100.6044	$100.60	$100.60	$100.60
Purchase #3	$19.83	8.117%	$21.4396	$21.44	$21.45	$21.40
Purchase #4	$195.79	12.689%	$220.6338	$220.63	$220.65	$220.60
Purchase #5	$140.26	3.167%	$144.702	$144.70	$144.70	$144.70
Purchase #6	$230.31	11.164%	$256.0218	$256.02	$256.00	$256.00
Purchase #7	$119.59	9.594%	$131.0635	$131.06	$131.05	$131.10
7 purchase totals =	$928.76		$1,012.3781	$1,012.36	$1,012.35	$1,012.30