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	$119.71	6.357%	$127.32	$127.32	$127.30	$127.30
Purchase #2	$121.98	8.457%	$132.2958	$132.30	$132.30	$132.30
Purchase #3	$85.63	10.301%	$94.4507	$94.45	$94.45	$94.50
Purchase #4	$125.29	9.363%	$137.0209	$137.02	$137.00	$137.00
Purchase #5	$31.40	11.491%	$35.0082	$35.01	$35.00	$35.00
Purchase #6	$147.96	3.725%	$153.4715	$153.47	$153.45	$153.50
Purchase #7	$218.92	4.261%	$228.2482	$228.25	$228.25	$228.20
7 purchase totals =	$850.89		$907.8153	$907.82	$907.75	$907.80