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	$133.69	7.330%	$143.4895	$143.49	$143.50	$143.50
Purchase #2	$65.68	11.151%	$73.004	$73.00	$73.00	$73.00
Purchase #3	$135.97	11.672%	$151.8404	$151.84	$151.85	$151.80
Purchase #4	$100.88	10.587%	$111.5602	$111.56	$111.55	$111.60
Purchase #5	$38.91	8.144%	$42.0788	$42.08	$42.10	$42.10
Purchase #6	$179.49	6.137%	$190.5053	$190.51	$190.50	$190.50
Purchase #7	$40.99	7.219%	$43.9491	$43.95	$43.95	$43.90
7 purchase totals =	$695.61		$756.4273	$756.43	$756.45	$756.40