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	$93.66	10.220%	$103.2321	$103.23	$103.25	$103.20
Purchase #2	$197.31	8.421%	$213.9255	$213.93	$213.95	$213.90
Purchase #3	$44.27	9.748%	$48.5854	$48.59	$48.60	$48.60
Purchase #4	$133.95	7.302%	$143.731	$143.73	$143.75	$143.70
Purchase #5	$68.54	5.541%	$72.3378	$72.34	$72.35	$72.30
Purchase #6	$121.34	5.369%	$127.8547	$127.85	$127.85	$127.90
Purchase #7	$167.81	13.191%	$189.9458	$189.95	$189.95	$189.90
7 purchase totals =	$826.88		$899.6123	$899.62	$899.70	$899.50