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	$194.43	11.173%	$216.1537	$216.15	$216.15	$216.20
Purchase #2	$240.46	9.229%	$262.6521	$262.65	$262.65	$262.70
Purchase #3	$88.75	11.804%	$99.2261	$99.23	$99.25	$99.20
Purchase #4	$86.90	3.857%	$90.2517	$90.25	$90.25	$90.30
Purchase #5	$159.65	3.108%	$164.6119	$164.61	$164.60	$164.60
Purchase #6	$41.51	13.337%	$47.0462	$47.05	$47.05	$47.00
Purchase #7	$194.46	3.205%	$200.6924	$200.69	$200.70	$200.70
7 purchase totals =	$1,006.16		$1,080.6341	$1,080.63	$1,080.65	$1,080.70