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	$231.91	4.353%	$242.005	$242.01	$242.00	$242.00
Purchase #2	$248.65	3.190%	$256.5819	$256.58	$256.60	$256.60
Purchase #3	$156.97	12.412%	$176.4531	$176.45	$176.45	$176.50
Purchase #4	$87.65	8.136%	$94.7812	$94.78	$94.80	$94.80
Purchase #5	$27.65	5.740%	$29.2371	$29.24	$29.25	$29.20
Purchase #6	$173.41	10.498%	$191.6146	$191.61	$191.60	$191.60
Purchase #7	$200.80	4.627%	$210.091	$210.09	$210.10	$210.10
7 purchase totals =	$1,127.04		$1,200.7639	$1,200.76	$1,200.80	$1,200.80