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	$104.72	10.862%	$116.0947	$116.09	$116.10	$116.10
Purchase #2	$89.81	8.616%	$97.548	$97.55	$97.55	$97.50
Purchase #3	$134.49	5.323%	$141.6489	$141.65	$141.65	$141.60
Purchase #4	$239.60	9.856%	$263.215	$263.22	$263.20	$263.20
Purchase #5	$81.88	11.597%	$91.3756	$91.38	$91.40	$91.40
Purchase #6	$85.55	8.623%	$92.927	$92.93	$92.95	$92.90
Purchase #7	$141.56	7.294%	$151.8854	$151.89	$151.90	$151.90
7 purchase totals =	$877.61		$954.6946	$954.71	$954.75	$954.60