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	$183.29	4.259%	$191.0963	$191.10	$191.10	$191.10
Purchase #2	$43.47	5.834%	$46.006	$46.01	$46.00	$46.00
Purchase #3	$73.25	7.172%	$78.5035	$78.50	$78.50	$78.50
Purchase #4	$200.51	7.677%	$215.9032	$215.90	$215.90	$215.90
Purchase #5	$68.61	6.719%	$73.2199	$73.22	$73.20	$73.20
Purchase #6	$142.97	10.384%	$157.816	$157.82	$157.80	$157.80
Purchase #7	$234.84	3.312%	$242.6179	$242.62	$242.60	$242.60
7 purchase totals =	$946.94		$1,005.1628	$1,005.17	$1,005.10	$1,005.10