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	$27.61	6.852%	$29.5018	$29.50	$29.50	$29.50
Purchase #2	$30.38	4.139%	$31.6374	$31.64	$31.65	$31.60
Purchase #3	$64.70	12.459%	$72.761	$72.76	$72.75	$72.80
Purchase #4	$92.50	13.612%	$105.0911	$105.09	$105.10	$105.10
Purchase #5	$7.68	10.854%	$8.5136	$8.51	$8.50	$8.50
Purchase #6	$74.53	5.133%	$78.3556	$78.36	$78.35	$78.40
Purchase #7	$27.74	4.303%	$28.9337	$28.93	$28.95	$28.90
7 purchase totals =	$325.14		$354.7942	$354.79	$354.80	$354.80