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	$156.55	6.843%	$167.2627	$167.26	$167.25	$167.30
Purchase #2	$183.41	4.856%	$192.3164	$192.32	$192.30	$192.30
Purchase #3	$81.31	6.861%	$86.8887	$86.89	$86.90	$86.90
Purchase #4	$166.88	5.589%	$176.2069	$176.21	$176.20	$176.20
Purchase #5	$125.65	5.493%	$132.552	$132.55	$132.55	$132.60
Purchase #6	$164.57	4.626%	$172.183	$172.18	$172.20	$172.20
Purchase #7	$53.94	10.423%	$59.5622	$59.56	$59.55	$59.60
7 purchase totals =	$932.31		$986.9719	$986.97	$986.95	$987.10