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	$93.94	9.632%	$102.9883	$102.99	$103.00	$103.00
Purchase #2	$150.91	3.431%	$156.0877	$156.09	$156.10	$156.10
Purchase #3	$80.61	11.176%	$89.619	$89.62	$89.60	$89.60
Purchase #4	$56.65	10.545%	$62.6237	$62.62	$62.60	$62.60
Purchase #5	$130.44	12.108%	$146.2337	$146.23	$146.25	$146.20
Purchase #6	$77.48	3.828%	$80.4459	$80.45	$80.45	$80.40
Purchase #7	$108.64	9.138%	$118.5675	$118.57	$118.55	$118.60
7 purchase totals =	$698.67		$756.5658	$756.57	$756.55	$756.50