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	$94.67	11.280%	$105.3488	$105.35	$105.35	$105.30
Purchase #2	$144.85	12.150%	$162.4493	$162.45	$162.45	$162.40
Purchase #3	$138.44	5.849%	$146.5374	$146.54	$146.55	$146.50
Purchase #4	$34.44	5.370%	$36.2894	$36.29	$36.30	$36.30
Purchase #5	$86.82	3.725%	$90.054	$90.05	$90.05	$90.10
Purchase #6	$66.46	4.546%	$69.4813	$69.48	$69.50	$69.50
Purchase #7	$44.81	3.728%	$46.4805	$46.48	$46.50	$46.50
7 purchase totals =	$610.49		$656.6407	$656.64	$656.70	$656.60