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	$193.42	7.735%	$208.381	$208.38	$208.40	$208.40
Purchase #2	$118.97	9.725%	$130.5398	$130.54	$130.55	$130.50
Purchase #3	$202.74	11.255%	$225.5584	$225.56	$225.55	$225.60
Purchase #4	$41.49	9.111%	$45.2702	$45.27	$45.25	$45.30
Purchase #5	$141.61	7.309%	$151.9603	$151.96	$151.95	$152.00
Purchase #6	$217.87	7.214%	$233.5871	$233.59	$233.60	$233.60
Purchase #7	$23.62	4.447%	$24.6704	$24.67	$24.65	$24.70
7 purchase totals =	$939.72		$1,019.9672	$1,019.97	$1,019.95	$1,020.10