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	$62.29	4.575%	$65.1398	$65.14	$65.15	$65.10
Purchase #2	$26.49	5.499%	$27.9467	$27.95	$27.95	$27.90
Purchase #3	$111.42	4.512%	$116.4473	$116.45	$116.45	$116.40
Purchase #4	$46.29	5.606%	$48.885	$48.89	$48.90	$48.90
Purchase #5	$142.73	6.355%	$151.8005	$151.80	$151.80	$151.80
Purchase #6	$207.50	4.534%	$216.9081	$216.91	$216.90	$216.90
Purchase #7	$197.78	6.442%	$210.521	$210.52	$210.50	$210.50
7 purchase totals =	$794.50		$837.6484	$837.66	$837.65	$837.50