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	$117.69	4.553%	$123.0484	$123.05	$123.05	$123.00
Purchase #2	$157.25	11.191%	$174.8478	$174.85	$174.85	$174.80
Purchase #3	$202.77	3.593%	$210.0555	$210.06	$210.05	$210.10
Purchase #4	$211.61	5.671%	$223.6104	$223.61	$223.60	$223.60
Purchase #5	$97.91	3.680%	$101.5131	$101.51	$101.50	$101.50
Purchase #6	$153.88	10.368%	$169.8343	$169.83	$169.85	$169.80
Purchase #7	$51.61	8.490%	$55.9917	$55.99	$56.00	$56.00
7 purchase totals =	$992.72		$1,058.9012	$1,058.90	$1,058.90	$1,058.80