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	$139.59	4.390%	$145.718	$145.72	$145.70	$145.70
Purchase #2	$129.86	10.410%	$143.3784	$143.38	$143.40	$143.40
Purchase #3	$163.28	9.345%	$178.5385	$178.54	$178.55	$178.50
Purchase #4	$165.29	4.590%	$172.8768	$172.88	$172.90	$172.90
Purchase #5	$134.66	13.333%	$152.6142	$152.61	$152.60	$152.60
Purchase #6	$176.77	5.815%	$187.0492	$187.05	$187.05	$187.00
Purchase #7	$155.99	5.368%	$164.3635	$164.36	$164.35	$164.40
7 purchase totals =	$1,065.44		$1,144.5386	$1,144.54	$1,144.55	$1,144.50