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	$52.82	4.764%	$55.3363	$55.34	$55.35	$55.30
Purchase #2	$238.59	7.740%	$257.0569	$257.06	$257.05	$257.10
Purchase #3	$156.26	10.286%	$172.3329	$172.33	$172.35	$172.30
Purchase #4	$192.60	4.108%	$200.512	$200.51	$200.50	$200.50
Purchase #5	$61.77	10.473%	$68.2392	$68.24	$68.25	$68.20
Purchase #6	$153.47	12.771%	$173.0697	$173.07	$173.05	$173.10
Purchase #7	$123.82	10.262%	$136.5264	$136.53	$136.55	$136.50
7 purchase totals =	$979.33		$1,063.0734	$1,063.08	$1,063.10	$1,063.00