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	$98.32	12.739%	$110.845	$110.85	$110.85	$110.80
Purchase #2	$162.29	5.734%	$171.5957	$171.60	$171.60	$171.60
Purchase #3	$100.63	11.196%	$111.8965	$111.90	$111.90	$111.90
Purchase #4	$31.98	4.161%	$33.3107	$33.31	$33.30	$33.30
Purchase #5	$110.38	10.553%	$122.0284	$122.03	$122.05	$122.00
Purchase #6	$202.85	3.786%	$210.5299	$210.53	$210.55	$210.50
Purchase #7	$158.75	9.441%	$173.7376	$173.74	$173.75	$173.70
7 purchase totals =	$865.20		$933.9438	$933.96	$934.00	$933.80