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	$183.65	11.515%	$204.7973	$204.80	$204.80	$204.80
Purchase #2	$190.98	4.654%	$199.8682	$199.87	$199.85	$199.90
Purchase #3	$187.89	4.638%	$196.6043	$196.60	$196.60	$196.60
Purchase #4	$41.38	6.141%	$43.9211	$43.92	$43.90	$43.90
Purchase #5	$44.62	8.827%	$48.5586	$48.56	$48.55	$48.60
Purchase #6	$31.47	9.546%	$34.4741	$34.47	$34.45	$34.50
Purchase #7	$140.86	9.292%	$153.9487	$153.95	$153.95	$153.90
7 purchase totals =	$820.85		$882.1723	$882.17	$882.10	$882.20