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	$114.90	10.120%	$126.5279	$126.53	$126.55	$126.50
Purchase #2	$90.64	10.243%	$99.9243	$99.92	$99.90	$99.90
Purchase #3	$230.38	4.825%	$241.4958	$241.50	$241.50	$241.50
Purchase #4	$57.86	8.627%	$62.8516	$62.85	$62.85	$62.90
Purchase #5	$134.40	7.836%	$144.9316	$144.93	$144.95	$144.90
Purchase #6	$168.41	10.767%	$186.5427	$186.54	$186.55	$186.50
Purchase #7	$7.53	10.739%	$8.3386	$8.34	$8.35	$8.30
7 purchase totals =	$804.12		$870.6125	$870.61	$870.65	$870.50