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	$55.83	7.259%	$59.8827	$59.88	$59.90	$59.90
Purchase #2	$104.25	8.513%	$113.1248	$113.12	$113.10	$113.10
Purchase #3	$154.72	5.583%	$163.358	$163.36	$163.35	$163.40
Purchase #4	$153.98	12.728%	$173.5786	$173.58	$173.60	$173.60
Purchase #5	$206.81	7.599%	$222.5255	$222.53	$222.55	$222.50
Purchase #6	$38.94	11.368%	$43.3667	$43.37	$43.35	$43.40
Purchase #7	$176.72	6.340%	$187.924	$187.92	$187.90	$187.90
7 purchase totals =	$891.25		$963.7603	$963.76	$963.75	$963.80