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	$205.33	12.315%	$230.6164	$230.62	$230.60	$230.60
Purchase #2	$220.80	3.169%	$227.7972	$227.80	$227.80	$227.80
Purchase #3	$154.88	11.607%	$172.8569	$172.86	$172.85	$172.90
Purchase #4	$160.38	4.461%	$167.5346	$167.53	$167.55	$167.50
Purchase #5	$82.95	7.807%	$89.4259	$89.43	$89.45	$89.40
Purchase #6	$53.87	4.288%	$56.1799	$56.18	$56.20	$56.20
Purchase #7	$157.43	6.517%	$167.6897	$167.69	$167.70	$167.70
7 purchase totals =	$1,035.64		$1,112.1006	$1,112.11	$1,112.15	$1,112.10