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	$124.97	9.235%	$136.511	$136.51	$136.50	$136.50
Purchase #2	$159.98	7.235%	$171.5546	$171.55	$171.55	$171.60
Purchase #3	$240.32	13.356%	$272.4171	$272.42	$272.40	$272.40
Purchase #4	$44.93	5.715%	$47.4977	$47.50	$47.50	$47.50
Purchase #5	$178.88	8.706%	$194.4533	$194.45	$194.45	$194.50
Purchase #6	$59.39	7.445%	$63.8116	$63.81	$63.80	$63.80
Purchase #7	$164.69	12.532%	$185.329	$185.33	$185.35	$185.30
7 purchase totals =	$973.16		$1,071.5743	$1,071.57	$1,071.55	$1,071.60