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	$181.64	9.523%	$198.9376	$198.94	$198.95	$198.90
Purchase #2	$67.59	7.304%	$72.5268	$72.53	$72.55	$72.50
Purchase #3	$241.34	6.515%	$257.0633	$257.06	$257.05	$257.10
Purchase #4	$235.81	6.837%	$251.9323	$251.93	$251.95	$251.90
Purchase #5	$59.61	11.601%	$66.5254	$66.53	$66.55	$66.50
Purchase #6	$82.65	10.368%	$91.2192	$91.22	$91.20	$91.20
Purchase #7	$241.31	10.859%	$267.5139	$267.51	$267.50	$267.50
7 purchase totals =	$1,109.95		$1,205.7185	$1,205.72	$1,205.75	$1,205.60