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	$228.50	13.448%	$259.2287	$259.23	$259.25	$259.20
Purchase #2	$24.38	13.855%	$27.7578	$27.76	$27.75	$27.80
Purchase #3	$88.65	6.507%	$94.4185	$94.42	$94.40	$94.40
Purchase #4	$127.48	4.458%	$133.1631	$133.16	$133.15	$133.20
Purchase #5	$57.72	6.681%	$61.5763	$61.58	$61.60	$61.60
Purchase #6	$173.30	13.397%	$196.517	$196.52	$196.50	$196.50
Purchase #7	$138.85	12.359%	$156.0105	$156.01	$156.00	$156.00
7 purchase totals =	$838.88		$928.6719	$928.68	$928.65	$928.70