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	$156.67	3.832%	$162.6736	$162.67	$162.65	$162.70
Purchase #2	$240.96	4.638%	$252.1357	$252.14	$252.15	$252.10
Purchase #3	$90.32	13.455%	$102.4726	$102.47	$102.45	$102.50
Purchase #4	$244.43	4.256%	$254.8329	$254.83	$254.85	$254.80
Purchase #5	$38.71	12.300%	$43.4713	$43.47	$43.45	$43.50
Purchase #6	$114.64	11.845%	$128.2191	$128.22	$128.20	$128.20
Purchase #7	$152.26	10.323%	$167.9778	$167.98	$168.00	$168.00
7 purchase totals =	$1,037.99		$1,111.7830	$1,111.78	$1,111.75	$1,111.80