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	$167.61	11.738%	$187.2841	$187.28	$187.30	$187.30
Purchase #2	$140.41	9.784%	$154.1477	$154.15	$154.15	$154.10
Purchase #3	$176.41	5.768%	$186.5853	$186.59	$186.60	$186.60
Purchase #4	$121.50	9.546%	$133.0984	$133.10	$133.10	$133.10
Purchase #5	$95.54	13.138%	$108.092	$108.09	$108.10	$108.10
Purchase #6	$171.46	11.273%	$190.7887	$190.79	$190.80	$190.80
Purchase #7	$207.73	13.624%	$236.0311	$236.03	$236.05	$236.00
7 purchase totals =	$1,080.66		$1,196.0273	$1,196.03	$1,196.10	$1,196.00