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	$137.42	13.236%	$155.6089	$155.61	$155.60	$155.60
Purchase #2	$17.87	8.179%	$19.3316	$19.33	$19.35	$19.30
Purchase #3	$82.79	3.762%	$85.9046	$85.90	$85.90	$85.90
Purchase #4	$126.58	5.147%	$133.0951	$133.10	$133.10	$133.10
Purchase #5	$75.47	8.787%	$82.1015	$82.10	$82.10	$82.10
Purchase #6	$242.78	10.613%	$268.5462	$268.55	$268.55	$268.50
Purchase #7	$216.25	4.311%	$225.5725	$225.57	$225.55	$225.60
7 purchase totals =	$899.16		$970.1604	$970.16	$970.15	$970.10