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	$223.65	9.820%	$245.6124	$245.61	$245.60	$245.60
Purchase #2	$238.56	7.234%	$255.8174	$255.82	$255.80	$255.80
Purchase #3	$228.60	12.404%	$256.9555	$256.96	$256.95	$257.00
Purchase #4	$18.52	12.790%	$20.8887	$20.89	$20.90	$20.90
Purchase #5	$145.50	11.382%	$162.0608	$162.06	$162.05	$162.10
Purchase #6	$233.40	8.123%	$252.3591	$252.36	$252.35	$252.40
Purchase #7	$175.51	4.451%	$183.322	$183.32	$183.30	$183.30
7 purchase totals =	$1,263.74		$1,377.0159	$1,377.02	$1,376.95	$1,377.10