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	$118.82	10.848%	$131.7096	$131.71	$131.70	$131.70
Purchase #2	$135.93	10.569%	$150.2964	$150.30	$150.30	$150.30
Purchase #3	$91.25	3.418%	$94.3689	$94.37	$94.35	$94.40
Purchase #4	$214.25	4.698%	$224.3155	$224.32	$224.30	$224.30
Purchase #5	$45.50	8.799%	$49.5035	$49.50	$49.50	$49.50
Purchase #6	$47.58	12.691%	$53.6184	$53.62	$53.60	$53.60
Purchase #7	$144.57	9.710%	$158.6077	$158.61	$158.60	$158.60
7 purchase totals =	$797.90		$862.4200	$862.43	$862.35	$862.40