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	$51.28	8.565%	$55.6721	$55.67	$55.65	$55.70
Purchase #2	$92.43	12.405%	$103.8959	$103.90	$103.90	$103.90
Purchase #3	$50.95	7.151%	$54.5934	$54.59	$54.60	$54.60
Purchase #4	$142.40	9.429%	$155.8269	$155.83	$155.85	$155.80
Purchase #5	$78.47	9.664%	$86.0533	$86.05	$86.05	$86.10
Purchase #6	$164.69	8.847%	$179.2601	$179.26	$179.25	$179.30
Purchase #7	$200.82	5.282%	$211.4273	$211.43	$211.45	$211.40
7 purchase totals =	$781.04		$846.7290	$846.73	$846.75	$846.80