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	$245.30	4.649%	$256.704	$256.70	$256.70	$256.70
Purchase #2	$105.26	3.104%	$108.5273	$108.53	$108.55	$108.50
Purchase #3	$10.38	13.871%	$11.8198	$11.82	$11.80	$11.80
Purchase #4	$9.71	3.153%	$10.0162	$10.02	$10.00	$10.00
Purchase #5	$83.70	8.449%	$90.7718	$90.77	$90.75	$90.80
Purchase #6	$78.41	12.274%	$88.034	$88.03	$88.05	$88.00
Purchase #7	$40.26	5.774%	$42.5846	$42.58	$42.60	$42.60
7 purchase totals =	$573.02		$608.4577	$608.45	$608.45	$608.40