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	$213.79	6.541%	$227.774	$227.77	$227.75	$227.80
Purchase #2	$43.59	11.860%	$48.7598	$48.76	$48.75	$48.80
Purchase #3	$157.78	11.649%	$176.1598	$176.16	$176.15	$176.20
Purchase #4	$80.43	11.527%	$89.7012	$89.70	$89.70	$89.70
Purchase #5	$79.53	4.197%	$82.8679	$82.87	$82.85	$82.90
Purchase #6	$176.92	3.183%	$182.5514	$182.55	$182.55	$182.60
Purchase #7	$177.48	10.685%	$196.4437	$196.44	$196.45	$196.40
7 purchase totals =	$929.52		$1,004.2578	$1,004.25	$1,004.20	$1,004.40