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	$195.27	8.626%	$212.114	$212.11	$212.10	$212.10
Purchase #2	$237.50	7.401%	$255.0774	$255.08	$255.10	$255.10
Purchase #3	$109.71	5.667%	$115.9273	$115.93	$115.95	$115.90
Purchase #4	$126.36	3.763%	$131.1149	$131.11	$131.10	$131.10
Purchase #5	$221.93	8.176%	$240.075	$240.08	$240.10	$240.10
Purchase #6	$230.52	10.326%	$254.3235	$254.32	$254.30	$254.30
Purchase #7	$38.89	8.205%	$42.0809	$42.08	$42.10	$42.10
7 purchase totals =	$1,160.18		$1,250.7130	$1,250.71	$1,250.75	$1,250.70