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	$224.46	10.320%	$247.6243	$247.62	$247.60	$247.60
Purchase #2	$156.75	6.277%	$166.5892	$166.59	$166.60	$166.60
Purchase #3	$104.97	6.235%	$111.5149	$111.51	$111.50	$111.50
Purchase #4	$12.55	11.602%	$14.0061	$14.01	$14.00	$14.00
Purchase #5	$215.61	8.583%	$234.1158	$234.12	$234.10	$234.10
Purchase #6	$170.65	10.364%	$188.3362	$188.34	$188.35	$188.30
Purchase #7	$116.93	12.872%	$131.9812	$131.98	$132.00	$132.00
7 purchase totals =	$1,001.92		$1,094.1677	$1,094.17	$1,094.15	$1,094.10