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	$165.32	8.820%	$179.9012	$179.90	$179.90	$179.90
Purchase #2	$63.56	4.298%	$66.2918	$66.29	$66.30	$66.30
Purchase #3	$31.86	7.554%	$34.2667	$34.27	$34.25	$34.30
Purchase #4	$138.27	10.330%	$152.5533	$152.55	$152.55	$152.60
Purchase #5	$250.57	5.540%	$264.4516	$264.45	$264.45	$264.50
Purchase #6	$207.55	5.517%	$219.0005	$219.00	$219.00	$219.00
Purchase #7	$158.72	4.837%	$166.3973	$166.40	$166.40	$166.40
7 purchase totals =	$1,015.85		$1,082.8624	$1,082.86	$1,082.85	$1,083.00