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	$73.59	9.625%	$80.673	$80.67	$80.65	$80.70
Purchase #2	$202.79	9.598%	$222.2538	$222.25	$222.25	$222.30
Purchase #3	$83.89	5.447%	$88.4595	$88.46	$88.45	$88.50
Purchase #4	$128.29	13.613%	$145.7541	$145.75	$145.75	$145.80
Purchase #5	$61.99	6.175%	$65.8179	$65.82	$65.80	$65.80
Purchase #6	$234.52	4.404%	$244.8483	$244.85	$244.85	$244.80
Purchase #7	$211.92	3.246%	$218.7989	$218.80	$218.80	$218.80
7 purchase totals =	$996.99		$1,066.6055	$1,066.60	$1,066.55	$1,066.70