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	$98.67	13.400%	$111.8918	$111.89	$111.90	$111.90
Purchase #2	$238.43	7.740%	$256.8845	$256.88	$256.90	$256.90
Purchase #3	$11.33	5.776%	$11.9844	$11.98	$12.00	$12.00
Purchase #4	$67.54	4.557%	$70.6178	$70.62	$70.60	$70.60
Purchase #5	$77.94	11.428%	$86.847	$86.85	$86.85	$86.80
Purchase #6	$122.46	3.461%	$126.6983	$126.70	$126.70	$126.70
Purchase #7	$40.93	11.546%	$45.6558	$45.66	$45.65	$45.70
7 purchase totals =	$657.30		$710.5796	$710.58	$710.60	$710.60