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	$42.62	4.328%	$44.4646	$44.46	$44.45	$44.50
Purchase #2	$64.31	3.320%	$66.4451	$66.45	$66.45	$66.40
Purchase #3	$94.29	11.531%	$105.1626	$105.16	$105.15	$105.20
Purchase #4	$15.85	11.151%	$17.6174	$17.62	$17.60	$17.60
Purchase #5	$114.76	7.617%	$123.5013	$123.50	$123.50	$123.50
Purchase #6	$134.47	10.166%	$148.1402	$148.14	$148.15	$148.10
Purchase #7	$163.57	4.819%	$171.4524	$171.45	$171.45	$171.50
7 purchase totals =	$629.87		$676.7836	$676.78	$676.75	$676.80