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	$190.47	4.842%	$199.6926	$199.69	$199.70	$199.70
Purchase #2	$130.58	5.407%	$137.6405	$137.64	$137.65	$137.60
Purchase #3	$228.60	13.237%	$258.8598	$258.86	$258.85	$258.90
Purchase #4	$100.52	5.308%	$105.8556	$105.86	$105.85	$105.90
Purchase #5	$142.61	3.338%	$147.3703	$147.37	$147.35	$147.40
Purchase #6	$213.81	12.824%	$241.229	$241.23	$241.25	$241.20
Purchase #7	$227.71	11.755%	$254.4773	$254.48	$254.50	$254.50
7 purchase totals =	$1,234.30		$1,345.1251	$1,345.13	$1,345.15	$1,345.20