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	$41.34	6.340%	$43.961	$43.96	$43.95	$44.00
Purchase #2	$37.65	7.866%	$40.6115	$40.61	$40.60	$40.60
Purchase #3	$154.85	3.318%	$159.9879	$159.99	$160.00	$160.00
Purchase #4	$26.38	5.578%	$27.8515	$27.85	$27.85	$27.90
Purchase #5	$42.56	5.192%	$44.7697	$44.77	$44.75	$44.80
Purchase #6	$131.52	8.663%	$142.9136	$142.91	$142.90	$142.90
Purchase #7	$40.35	7.558%	$43.3997	$43.40	$43.40	$43.40
7 purchase totals =	$474.65		$503.4949	$503.49	$503.45	$503.60