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	$23.83	4.314%	$24.858	$24.86	$24.85	$24.90
Purchase #2	$94.38	12.403%	$106.086	$106.09	$106.10	$106.10
Purchase #3	$230.52	13.735%	$262.1819	$262.18	$262.20	$262.20
Purchase #4	$148.74	5.648%	$157.1408	$157.14	$157.15	$157.10
Purchase #5	$72.95	9.683%	$80.0137	$80.01	$80.00	$80.00
Purchase #6	$145.32	13.318%	$164.6737	$164.67	$164.65	$164.70
Purchase #7	$112.42	13.463%	$127.5551	$127.56	$127.55	$127.60
7 purchase totals =	$828.16		$922.5092	$922.51	$922.50	$922.60