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	$140.35	11.490%	$156.4762	$156.48	$156.50	$156.50
Purchase #2	$117.70	11.470%	$131.2002	$131.20	$131.20	$131.20
Purchase #3	$44.73	8.768%	$48.6519	$48.65	$48.65	$48.70
Purchase #4	$163.48	3.339%	$168.9386	$168.94	$168.95	$168.90
Purchase #5	$201.25	10.549%	$222.4799	$222.48	$222.50	$222.50
Purchase #6	$17.73	10.235%	$19.5447	$19.54	$19.55	$19.50
Purchase #7	$241.77	11.704%	$270.0668	$270.07	$270.05	$270.10
7 purchase totals =	$927.01		$1,017.3583	$1,017.36	$1,017.40	$1,017.40