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	$30.81	8.640%	$33.472	$33.47	$33.45	$33.50
Purchase #2	$216.93	11.219%	$241.2674	$241.27	$241.25	$241.30
Purchase #3	$46.89	3.811%	$48.677	$48.68	$48.70	$48.70
Purchase #4	$192.90	13.772%	$219.4662	$219.47	$219.45	$219.50
Purchase #5	$174.73	9.613%	$191.5268	$191.53	$191.55	$191.50
Purchase #6	$98.27	6.835%	$104.9868	$104.99	$105.00	$105.00
Purchase #7	$153.74	9.404%	$168.1977	$168.20	$168.20	$168.20
7 purchase totals =	$914.27		$1,007.5939	$1,007.61	$1,007.60	$1,007.70