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	$39.69	9.817%	$43.5864	$43.59	$43.60	$43.60
Purchase #2	$17.63	4.841%	$18.4835	$18.48	$18.50	$18.50
Purchase #3	$15.56	13.259%	$17.6231	$17.62	$17.60	$17.60
Purchase #4	$154.87	8.726%	$168.384	$168.38	$168.40	$168.40
Purchase #5	$60.27	7.758%	$64.9457	$64.95	$64.95	$64.90
Purchase #6	$200.81	8.345%	$217.5676	$217.57	$217.55	$217.60
Purchase #7	$154.48	12.561%	$173.8842	$173.88	$173.90	$173.90
7 purchase totals =	$643.31		$704.4745	$704.47	$704.50	$704.50