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	$98.91	11.613%	$110.3964	$110.40	$110.40	$110.40
Purchase #2	$27.62	12.244%	$31.0018	$31.00	$31.00	$31.00
Purchase #3	$205.52	4.848%	$215.4836	$215.48	$215.50	$215.50
Purchase #4	$69.52	3.679%	$72.0776	$72.08	$72.10	$72.10
Purchase #5	$26.26	6.214%	$27.8918	$27.89	$27.90	$27.90
Purchase #6	$230.56	12.509%	$259.4008	$259.40	$259.40	$259.40
Purchase #7	$159.65	3.295%	$164.9105	$164.91	$164.90	$164.90
7 purchase totals =	$818.04		$881.1625	$881.16	$881.20	$881.20