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	$97.60	7.841%	$105.2528	$105.25	$105.25	$105.30
Purchase #2	$58.84	8.816%	$64.0273	$64.03	$64.05	$64.00
Purchase #3	$37.69	11.824%	$42.1465	$42.15	$42.15	$42.10
Purchase #4	$126.71	8.606%	$137.6147	$137.61	$137.60	$137.60
Purchase #5	$61.51	3.208%	$63.4832	$63.48	$63.50	$63.50
Purchase #6	$108.34	11.172%	$120.4437	$120.44	$120.45	$120.40
Purchase #7	$9.89	4.851%	$10.3698	$10.37	$10.35	$10.40
7 purchase totals =	$500.58		$543.3380	$543.33	$543.35	$543.30