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	$98.59	6.809%	$105.303	$105.30	$105.30	$105.30
Purchase #2	$113.85	8.742%	$123.8028	$123.80	$123.80	$123.80
Purchase #3	$163.72	3.636%	$169.6729	$169.67	$169.65	$169.70
Purchase #4	$244.25	4.741%	$255.8299	$255.83	$255.85	$255.80
Purchase #5	$26.36	5.679%	$27.857	$27.86	$27.85	$27.90
Purchase #6	$154.70	13.535%	$175.6386	$175.64	$175.65	$175.60
Purchase #7	$23.27	4.215%	$24.2508	$24.25	$24.25	$24.30
7 purchase totals =	$824.74		$882.3550	$882.35	$882.35	$882.40