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	$85.34	8.332%	$92.4505	$92.45	$92.45	$92.50
Purchase #2	$158.25	11.789%	$176.9061	$176.91	$176.90	$176.90
Purchase #3	$155.69	12.727%	$175.5047	$175.50	$175.50	$175.50
Purchase #4	$66.46	9.207%	$72.579	$72.58	$72.60	$72.60
Purchase #5	$223.42	12.524%	$251.4011	$251.40	$251.40	$251.40
Purchase #6	$164.55	5.863%	$174.1976	$174.20	$174.20	$174.20
Purchase #7	$179.69	5.658%	$189.8569	$189.86	$189.85	$189.90
7 purchase totals =	$1,033.40		$1,132.8959	$1,132.90	$1,132.90	$1,133.00