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	$131.32	7.844%	$141.6207	$141.62	$141.60	$141.60
Purchase #2	$95.38	8.651%	$103.6313	$103.63	$103.65	$103.60
Purchase #3	$97.54	5.162%	$102.575	$102.58	$102.60	$102.60
Purchase #4	$45.84	8.302%	$49.6456	$49.65	$49.65	$49.60
Purchase #5	$40.98	3.575%	$42.445	$42.45	$42.45	$42.40
Purchase #6	$173.77	7.584%	$186.9487	$186.95	$186.95	$186.90
Purchase #7	$179.93	11.575%	$200.7569	$200.76	$200.75	$200.80
7 purchase totals =	$764.76		$827.6232	$827.64	$827.65	$827.50