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	$187.90	3.725%	$194.8993	$194.90	$194.90	$194.90
Purchase #2	$167.28	7.599%	$179.9916	$179.99	$180.00	$180.00
Purchase #3	$167.96	3.139%	$173.2323	$173.23	$173.25	$173.20
Purchase #4	$240.31	9.616%	$263.4182	$263.42	$263.40	$263.40
Purchase #5	$65.77	9.648%	$72.1155	$72.12	$72.10	$72.10
Purchase #6	$87.39	10.388%	$96.4681	$96.47	$96.45	$96.50
Purchase #7	$84.33	5.644%	$89.0896	$89.09	$89.10	$89.10
7 purchase totals =	$1,000.94		$1,069.2146	$1,069.22	$1,069.20	$1,069.20