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	$203.73	13.301%	$230.8281	$230.83	$230.85	$230.80
Purchase #2	$43.53	3.600%	$45.0971	$45.10	$45.10	$45.10
Purchase #3	$124.31	12.363%	$139.6784	$139.68	$139.70	$139.70
Purchase #4	$163.38	6.682%	$174.2971	$174.30	$174.30	$174.30
Purchase #5	$52.70	6.831%	$56.2999	$56.30	$56.30	$56.30
Purchase #6	$230.46	4.862%	$241.665	$241.67	$241.65	$241.70
Purchase #7	$139.65	7.824%	$150.5762	$150.58	$150.60	$150.60
7 purchase totals =	$957.76		$1,038.4418	$1,038.46	$1,038.50	$1,038.50