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	$21.58	3.204%	$22.2714	$22.27	$22.25	$22.30
Purchase #2	$66.72	3.690%	$69.182	$69.18	$69.20	$69.20
Purchase #3	$13.38	6.659%	$14.271	$14.27	$14.25	$14.30
Purchase #4	$53.67	4.229%	$55.9397	$55.94	$55.95	$55.90
Purchase #5	$140.50	9.725%	$154.1636	$154.16	$154.15	$154.20
Purchase #6	$186.25	5.545%	$196.5776	$196.58	$196.60	$196.60
Purchase #7	$47.72	9.871%	$52.4304	$52.43	$52.45	$52.40
7 purchase totals =	$529.82		$564.8357	$564.83	$564.85	$564.90