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	$35.92	13.836%	$40.8899	$40.89	$40.90	$40.90
Purchase #2	$38.37	13.749%	$43.6455	$43.65	$43.65	$43.60
Purchase #3	$73.87	4.761%	$77.387	$77.39	$77.40	$77.40
Purchase #4	$230.71	13.457%	$261.7566	$261.76	$261.75	$261.80
Purchase #5	$233.46	11.304%	$259.8503	$259.85	$259.85	$259.90
Purchase #6	$119.40	5.661%	$126.1592	$126.16	$126.15	$126.20
Purchase #7	$173.50	7.499%	$186.5108	$186.51	$186.50	$186.50
7 purchase totals =	$905.23		$996.1993	$996.21	$996.20	$996.30