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	$133.27	11.633%	$148.7733	$148.77	$148.75	$148.80
Purchase #2	$138.80	12.868%	$156.6608	$156.66	$156.65	$156.70
Purchase #3	$73.81	10.432%	$81.5099	$81.51	$81.50	$81.50
Purchase #4	$227.63	6.113%	$241.545	$241.55	$241.55	$241.50
Purchase #5	$144.73	8.112%	$156.4705	$156.47	$156.45	$156.50
Purchase #6	$94.29	6.837%	$100.7366	$100.74	$100.75	$100.70
Purchase #7	$172.70	5.693%	$182.5318	$182.53	$182.55	$182.50
7 purchase totals =	$985.23		$1,068.2279	$1,068.23	$1,068.20	$1,068.20