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	$158.29	5.487%	$166.9754	$166.98	$167.00	$167.00
Purchase #2	$197.85	8.639%	$214.9423	$214.94	$214.95	$214.90
Purchase #3	$127.48	11.622%	$142.2957	$142.30	$142.30	$142.30
Purchase #4	$121.95	4.757%	$127.7512	$127.75	$127.75	$127.80
Purchase #5	$40.37	4.668%	$42.2545	$42.25	$42.25	$42.30
Purchase #6	$87.51	9.288%	$95.6379	$95.64	$95.65	$95.60
Purchase #7	$67.91	7.469%	$72.9822	$72.98	$73.00	$73.00
7 purchase totals =	$801.36		$862.8392	$862.84	$862.90	$862.90