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	$132.58	6.803%	$141.5994	$141.60	$141.60	$141.60
Purchase #2	$74.78	10.200%	$82.4076	$82.41	$82.40	$82.40
Purchase #3	$10.42	11.312%	$11.5987	$11.60	$11.60	$11.60
Purchase #4	$85.39	11.133%	$94.8965	$94.90	$94.90	$94.90
Purchase #5	$120.97	13.441%	$137.2296	$137.23	$137.25	$137.20
Purchase #6	$135.34	5.200%	$142.3777	$142.38	$142.40	$142.40
Purchase #7	$146.35	10.488%	$161.6992	$161.70	$161.70	$161.70
7 purchase totals =	$705.83		$771.8087	$771.82	$771.85	$771.80