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	$229.49	8.508%	$249.015	$249.02	$249.00	$249.00
Purchase #2	$192.67	3.872%	$200.1302	$200.13	$200.15	$200.10
Purchase #3	$49.25	9.284%	$53.8224	$53.82	$53.80	$53.80
Purchase #4	$85.70	6.554%	$91.3168	$91.32	$91.30	$91.30
Purchase #5	$153.90	12.157%	$172.6096	$172.61	$172.60	$172.60
Purchase #6	$102.62	6.699%	$109.4945	$109.49	$109.50	$109.50
Purchase #7	$154.94	4.124%	$161.3297	$161.33	$161.35	$161.30
7 purchase totals =	$968.57		$1,037.7182	$1,037.72	$1,037.70	$1,037.60