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	$156.61	4.134%	$163.0843	$163.08	$163.10	$163.10
Purchase #2	$210.44	7.123%	$225.4296	$225.43	$225.45	$225.40
Purchase #3	$172.38	9.275%	$188.3682	$188.37	$188.35	$188.40
Purchase #4	$123.52	13.776%	$140.5361	$140.54	$140.55	$140.50
Purchase #5	$104.64	6.157%	$111.0827	$111.08	$111.10	$111.10
Purchase #6	$172.53	10.750%	$191.077	$191.08	$191.10	$191.10
Purchase #7	$12.69	9.154%	$13.8516	$13.85	$13.85	$13.90
7 purchase totals =	$952.81		$1,033.4295	$1,033.43	$1,033.50	$1,033.50