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	$62.63	13.497%	$71.0832	$71.08	$71.10	$71.10
Purchase #2	$177.38	11.564%	$197.8922	$197.89	$197.90	$197.90
Purchase #3	$121.96	4.852%	$127.8775	$127.88	$127.90	$127.90
Purchase #4	$132.53	9.823%	$145.5484	$145.55	$145.55	$145.50
Purchase #5	$42.54	6.680%	$45.3817	$45.38	$45.40	$45.40
Purchase #6	$161.35	3.700%	$167.32	$167.32	$167.30	$167.30
Purchase #7	$139.36	8.718%	$151.5094	$151.51	$151.50	$151.50
7 purchase totals =	$837.75		$906.6124	$906.61	$906.65	$906.60