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	$183.82	6.738%	$196.2058	$196.21	$196.20	$196.20
Purchase #2	$101.37	9.537%	$111.0377	$111.04	$111.05	$111.00
Purchase #3	$74.66	13.118%	$84.4539	$84.45	$84.45	$84.50
Purchase #4	$173.35	11.275%	$192.8952	$192.90	$192.90	$192.90
Purchase #5	$135.79	13.852%	$154.5996	$154.60	$154.60	$154.60
Purchase #6	$235.69	10.166%	$259.6502	$259.65	$259.65	$259.70
Purchase #7	$126.96	3.685%	$131.6385	$131.64	$131.65	$131.60
7 purchase totals =	$1,031.64		$1,130.4809	$1,130.49	$1,130.50	$1,130.50