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	$145.62	6.395%	$154.9324	$154.93	$154.95	$154.90
Purchase #2	$79.73	8.563%	$86.5573	$86.56	$86.55	$86.60
Purchase #3	$221.53	5.400%	$233.4926	$233.49	$233.50	$233.50
Purchase #4	$176.58	10.152%	$194.5064	$194.51	$194.50	$194.50
Purchase #5	$37.32	12.154%	$41.8559	$41.86	$41.85	$41.90
Purchase #6	$12.74	9.764%	$13.9839	$13.98	$14.00	$14.00
Purchase #7	$63.45	11.730%	$70.8927	$70.89	$70.90	$70.90
7 purchase totals =	$736.97		$796.2212	$796.22	$796.25	$796.30