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	$178.89	11.387%	$199.2602	$199.26	$199.25	$199.30
Purchase #2	$65.83	8.584%	$71.4808	$71.48	$71.50	$71.50
Purchase #3	$230.55	5.651%	$243.5784	$243.58	$243.60	$243.60
Purchase #4	$143.74	6.691%	$153.3576	$153.36	$153.35	$153.40
Purchase #5	$179.85	10.240%	$198.2666	$198.27	$198.25	$198.30
Purchase #6	$17.58	11.684%	$19.634	$19.63	$19.65	$19.60
Purchase #7	$233.58	9.399%	$255.5342	$255.53	$255.55	$255.50
7 purchase totals =	$1,050.02		$1,141.1118	$1,141.11	$1,141.15	$1,141.20