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	$136.31	7.727%	$146.8427	$146.84	$146.85	$146.80
Purchase #2	$186.91	4.139%	$194.6462	$194.65	$194.65	$194.60
Purchase #3	$82.73	9.576%	$90.6522	$90.65	$90.65	$90.70
Purchase #4	$161.66	8.287%	$175.0568	$175.06	$175.05	$175.10
Purchase #5	$136.81	13.611%	$155.4312	$155.43	$155.45	$155.40
Purchase #6	$174.60	9.686%	$191.5118	$191.51	$191.50	$191.50
Purchase #7	$178.71	12.113%	$200.3571	$200.36	$200.35	$200.40
7 purchase totals =	$1,057.73		$1,154.4980	$1,154.50	$1,154.50	$1,154.50