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	$241.65	10.330%	$266.6124	$266.61	$266.60	$266.60
Purchase #2	$58.88	13.627%	$66.9036	$66.90	$66.90	$66.90
Purchase #3	$117.55	5.418%	$123.9189	$123.92	$123.90	$123.90
Purchase #4	$108.49	5.511%	$114.4689	$114.47	$114.45	$114.50
Purchase #5	$141.53	4.696%	$148.1762	$148.18	$148.20	$148.20
Purchase #6	$250.61	6.330%	$266.4736	$266.47	$266.45	$266.50
Purchase #7	$98.62	10.205%	$108.6842	$108.68	$108.70	$108.70
7 purchase totals =	$1,017.33		$1,095.2378	$1,095.23	$1,095.20	$1,095.30