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	$142.93	4.390%	$149.2046	$149.20	$149.20	$149.20
Purchase #2	$154.50	6.498%	$164.5394	$164.54	$164.55	$164.50
Purchase #3	$163.82	6.255%	$174.0669	$174.07	$174.05	$174.10
Purchase #4	$13.57	7.142%	$14.5392	$14.54	$14.55	$14.50
Purchase #5	$204.89	5.188%	$215.5197	$215.52	$215.50	$215.50
Purchase #6	$165.45	4.339%	$172.6289	$172.63	$172.65	$172.60
Purchase #7	$61.31	5.348%	$64.5889	$64.59	$64.60	$64.60
7 purchase totals =	$906.47		$955.0876	$955.09	$955.10	$955.00