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	$231.55	10.478%	$255.8118	$255.81	$255.80	$255.80
Purchase #2	$64.29	13.237%	$72.8001	$72.80	$72.80	$72.80
Purchase #3	$59.42	5.654%	$62.7796	$62.78	$62.80	$62.80
Purchase #4	$101.81	9.594%	$111.5777	$111.58	$111.60	$111.60
Purchase #5	$185.33	11.849%	$207.2898	$207.29	$207.30	$207.30
Purchase #6	$181.49	12.329%	$203.8659	$203.87	$203.85	$203.90
Purchase #7	$174.76	6.652%	$186.385	$186.39	$186.40	$186.40
7 purchase totals =	$998.65		$1,100.5099	$1,100.52	$1,100.55	$1,100.60