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	$143.49	7.325%	$154.0006	$154.00	$154.00	$154.00
Purchase #2	$226.85	7.281%	$243.3669	$243.37	$243.35	$243.40
Purchase #3	$46.62	10.724%	$51.6195	$51.62	$51.60	$51.60
Purchase #4	$185.39	10.566%	$204.9783	$204.98	$205.00	$205.00
Purchase #5	$51.82	4.647%	$54.2281	$54.23	$54.25	$54.20
Purchase #6	$84.78	7.173%	$90.8613	$90.86	$90.85	$90.90
Purchase #7	$198.72	10.582%	$219.7486	$219.75	$219.75	$219.70
7 purchase totals =	$937.67		$1,018.8033	$1,018.81	$1,018.80	$1,018.80