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	$238.78	10.418%	$263.6561	$263.66	$263.65	$263.70
Purchase #2	$195.25	13.702%	$222.0032	$222.00	$222.00	$222.00
Purchase #3	$57.64	13.824%	$65.6082	$65.61	$65.60	$65.60
Purchase #4	$234.88	13.266%	$266.0392	$266.04	$266.05	$266.00
Purchase #5	$58.32	10.170%	$64.2511	$64.25	$64.25	$64.30
Purchase #6	$101.86	9.137%	$111.1669	$111.17	$111.15	$111.20
Purchase #7	$23.93	7.638%	$25.7578	$25.76	$25.75	$25.80
7 purchase totals =	$910.66		$1,018.4825	$1,018.49	$1,018.45	$1,018.60