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	$155.79	10.739%	$172.5203	$172.52	$172.50	$172.50
Purchase #2	$192.72	8.395%	$208.8988	$208.90	$208.90	$208.90
Purchase #3	$25.54	5.269%	$26.8857	$26.89	$26.90	$26.90
Purchase #4	$107.42	3.465%	$111.1421	$111.14	$111.15	$111.10
Purchase #5	$176.84	11.131%	$196.5241	$196.52	$196.50	$196.50
Purchase #6	$152.96	3.835%	$158.826	$158.83	$158.85	$158.80
Purchase #7	$159.57	12.479%	$179.4827	$179.48	$179.50	$179.50
7 purchase totals =	$970.84		$1,054.2797	$1,054.28	$1,054.30	$1,054.20