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	$188.38	9.564%	$206.3967	$206.40	$206.40	$206.40
Purchase #2	$183.70	3.141%	$189.47	$189.47	$189.45	$189.50
Purchase #3	$208.69	11.400%	$232.4807	$232.48	$232.50	$232.50
Purchase #4	$147.35	6.132%	$156.3855	$156.39	$156.40	$156.40
Purchase #5	$177.87	4.604%	$186.0591	$186.06	$186.05	$186.10
Purchase #6	$150.85	3.155%	$155.6093	$155.61	$155.60	$155.60
Purchase #7	$143.61	7.158%	$153.8896	$153.89	$153.90	$153.90
7 purchase totals =	$1,200.45		$1,280.2909	$1,280.30	$1,280.30	$1,280.40