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	$207.55	8.670%	$225.5446	$225.54	$225.55	$225.50
Purchase #2	$28.41	13.239%	$32.1712	$32.17	$32.15	$32.20
Purchase #3	$226.82	12.610%	$255.422	$255.42	$255.40	$255.40
Purchase #4	$138.73	4.576%	$145.0783	$145.08	$145.10	$145.10
Purchase #5	$208.89	10.264%	$230.3305	$230.33	$230.35	$230.30
Purchase #6	$174.79	3.738%	$181.3237	$181.32	$181.30	$181.30
Purchase #7	$183.32	6.278%	$194.8288	$194.83	$194.85	$194.80
7 purchase totals =	$1,168.51		$1,264.6991	$1,264.69	$1,264.70	$1,264.60