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	$166.47	6.244%	$176.8644	$176.86	$176.85	$176.90
Purchase #2	$130.78	4.761%	$137.0064	$137.01	$137.00	$137.00
Purchase #3	$42.90	12.650%	$48.3269	$48.33	$48.35	$48.30
Purchase #4	$201.36	8.792%	$219.0636	$219.06	$219.05	$219.10
Purchase #5	$113.86	12.354%	$127.9263	$127.93	$127.95	$127.90
Purchase #6	$87.75	5.117%	$92.2402	$92.24	$92.25	$92.20
Purchase #7	$211.79	13.505%	$240.3922	$240.39	$240.40	$240.40
7 purchase totals =	$954.91		$1,041.8200	$1,041.82	$1,041.85	$1,041.80