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	$215.79	3.245%	$222.7924	$222.79	$222.80	$222.80
Purchase #2	$53.91	4.874%	$56.5376	$56.54	$56.55	$56.50
Purchase #3	$206.37	3.149%	$212.8686	$212.87	$212.85	$212.90
Purchase #4	$217.51	13.174%	$246.1648	$246.16	$246.15	$246.20
Purchase #5	$117.39	3.760%	$121.8039	$121.80	$121.80	$121.80
Purchase #6	$177.97	10.578%	$196.7957	$196.80	$196.80	$196.80
Purchase #7	$51.96	10.754%	$57.5478	$57.55	$57.55	$57.50
7 purchase totals =	$1,040.90		$1,114.5108	$1,114.51	$1,114.50	$1,114.50