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	$45.97	12.256%	$51.6041	$51.60	$51.60	$51.60
Purchase #2	$9.34	12.642%	$10.5208	$10.52	$10.50	$10.50
Purchase #3	$245.69	3.638%	$254.6282	$254.63	$254.65	$254.60
Purchase #4	$96.52	11.448%	$107.5696	$107.57	$107.55	$107.60
Purchase #5	$61.85	7.477%	$66.4745	$66.47	$66.45	$66.50
Purchase #6	$79.30	9.322%	$86.6923	$86.69	$86.70	$86.70
Purchase #7	$240.72	6.199%	$255.6422	$255.64	$255.65	$255.60
7 purchase totals =	$779.39		$833.1317	$833.12	$833.10	$833.10