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	$176.48	3.181%	$182.0938	$182.09	$182.10	$182.10
Purchase #2	$125.96	6.479%	$134.1209	$134.12	$134.10	$134.10
Purchase #3	$113.75	8.420%	$123.3278	$123.33	$123.35	$123.30
Purchase #4	$132.79	5.865%	$140.5781	$140.58	$140.60	$140.60
Purchase #5	$94.64	10.853%	$104.9113	$104.91	$104.90	$104.90
Purchase #6	$167.55	3.177%	$172.8731	$172.87	$172.85	$172.90
Purchase #7	$133.82	6.777%	$142.889	$142.89	$142.90	$142.90
7 purchase totals =	$944.99		$1,000.7940	$1,000.79	$1,000.80	$1,000.80