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	$215.27	9.696%	$236.1426	$236.14	$236.15	$236.10
Purchase #2	$234.47	9.834%	$257.5278	$257.53	$257.55	$257.50
Purchase #3	$100.51	4.719%	$105.2531	$105.25	$105.25	$105.30
Purchase #4	$144.83	7.604%	$155.8429	$155.84	$155.85	$155.80
Purchase #5	$168.56	3.159%	$173.8848	$173.88	$173.90	$173.90
Purchase #6	$232.78	4.429%	$243.0898	$243.09	$243.10	$243.10
Purchase #7	$123.27	7.426%	$132.424	$132.42	$132.40	$132.40
7 purchase totals =	$1,219.69		$1,304.1650	$1,304.15	$1,304.20	$1,304.10