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	$168.56	11.588%	$188.0927	$188.09	$188.10	$188.10
Purchase #2	$122.51	4.758%	$128.339	$128.34	$128.35	$128.30
Purchase #3	$132.59	11.805%	$148.2422	$148.24	$148.25	$148.20
Purchase #4	$176.97	6.724%	$188.8695	$188.87	$188.85	$188.90
Purchase #5	$154.39	10.806%	$171.0734	$171.07	$171.05	$171.10
Purchase #6	$43.44	7.255%	$46.5916	$46.59	$46.60	$46.60
Purchase #7	$243.50	5.247%	$256.2764	$256.28	$256.30	$256.30
7 purchase totals =	$1,041.96		$1,127.4848	$1,127.48	$1,127.50	$1,127.50