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	$82.82	9.845%	$90.9736	$90.97	$90.95	$91.00
Purchase #2	$69.56	4.866%	$72.9448	$72.94	$72.95	$72.90
Purchase #3	$240.54	13.219%	$272.337	$272.34	$272.35	$272.30
Purchase #4	$192.81	4.746%	$201.9608	$201.96	$201.95	$202.00
Purchase #5	$169.93	7.733%	$183.0707	$183.07	$183.05	$183.10
Purchase #6	$178.73	9.765%	$196.183	$196.18	$196.20	$196.20
Purchase #7	$249.51	5.238%	$262.5793	$262.58	$262.60	$262.60
7 purchase totals =	$1,183.90		$1,280.0492	$1,280.04	$1,280.05	$1,280.10