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	$80.50	7.645%	$86.6542	$86.65	$86.65	$86.70
Purchase #2	$92.42	12.453%	$103.9291	$103.93	$103.95	$103.90
Purchase #3	$221.26	7.194%	$237.1774	$237.18	$237.20	$237.20
Purchase #4	$220.89	10.608%	$244.322	$244.32	$244.30	$244.30
Purchase #5	$132.78	5.686%	$140.3299	$140.33	$140.35	$140.30
Purchase #6	$92.37	9.188%	$100.857	$100.86	$100.85	$100.90
Purchase #7	$181.30	8.343%	$196.4259	$196.43	$196.45	$196.40
7 purchase totals =	$1,021.52		$1,109.6955	$1,109.70	$1,109.75	$1,109.70