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	$198.37	10.582%	$219.3615	$219.36	$219.35	$219.40
Purchase #2	$56.31	5.752%	$59.549	$59.55	$59.55	$59.50
Purchase #3	$247.75	3.525%	$256.4832	$256.48	$256.50	$256.50
Purchase #4	$140.99	3.202%	$145.5045	$145.50	$145.50	$145.50
Purchase #5	$246.29	5.378%	$259.5355	$259.54	$259.55	$259.50
Purchase #6	$146.58	13.710%	$166.6761	$166.68	$166.70	$166.70
Purchase #7	$209.73	13.716%	$238.4966	$238.50	$238.50	$238.50
7 purchase totals =	$1,246.02		$1,345.6064	$1,345.61	$1,345.65	$1,345.60