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	$156.47	13.400%	$177.437	$177.44	$177.45	$177.40
Purchase #2	$220.33	10.690%	$243.8833	$243.88	$243.90	$243.90
Purchase #3	$141.87	10.554%	$156.843	$156.84	$156.85	$156.80
Purchase #4	$48.61	10.606%	$53.7656	$53.77	$53.75	$53.80
Purchase #5	$235.88	8.769%	$256.5643	$256.56	$256.55	$256.60
Purchase #6	$157.60	12.187%	$176.8067	$176.81	$176.80	$176.80
Purchase #7	$136.28	11.272%	$151.6415	$151.64	$151.65	$151.60
7 purchase totals =	$1,097.04		$1,216.9414	$1,216.94	$1,216.95	$1,216.90