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	$111.85	9.664%	$122.6592	$122.66	$122.65	$122.70
Purchase #2	$163.55	13.485%	$185.6047	$185.60	$185.60	$185.60
Purchase #3	$64.51	3.732%	$66.9175	$66.92	$66.90	$66.90
Purchase #4	$139.80	9.131%	$152.5651	$152.57	$152.55	$152.60
Purchase #5	$138.32	3.790%	$143.5623	$143.56	$143.55	$143.60
Purchase #6	$181.96	4.135%	$189.484	$189.48	$189.50	$189.50
Purchase #7	$143.40	3.732%	$148.7517	$148.75	$148.75	$148.80
7 purchase totals =	$943.39		$1,009.5445	$1,009.54	$1,009.50	$1,009.70