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	$117.34	10.214%	$129.3251	$129.33	$129.35	$129.30
Purchase #2	$144.64	11.711%	$161.5788	$161.58	$161.60	$161.60
Purchase #3	$27.89	5.661%	$29.4689	$29.47	$29.45	$29.50
Purchase #4	$38.60	5.284%	$40.6396	$40.64	$40.65	$40.60
Purchase #5	$55.59	10.579%	$61.4709	$61.47	$61.45	$61.50
Purchase #6	$38.36	13.330%	$43.4734	$43.47	$43.45	$43.50
Purchase #7	$233.87	8.341%	$253.3771	$253.38	$253.40	$253.40
7 purchase totals =	$656.29		$719.3338	$719.34	$719.35	$719.40