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	$166.54	4.660%	$174.3008	$174.30	$174.30	$174.30
Purchase #2	$160.95	9.417%	$176.1067	$176.11	$176.10	$176.10
Purchase #3	$42.34	5.312%	$44.5891	$44.59	$44.60	$44.60
Purchase #4	$228.50	3.842%	$237.279	$237.28	$237.30	$237.30
Purchase #5	$137.90	12.680%	$155.3857	$155.39	$155.40	$155.40
Purchase #6	$230.93	10.553%	$255.3	$255.30	$255.30	$255.30
Purchase #7	$111.42	7.577%	$119.8623	$119.86	$119.85	$119.90
7 purchase totals =	$1,078.58		$1,162.8236	$1,162.83	$1,162.85	$1,162.90