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	$88.72	11.427%	$98.858	$98.86	$98.85	$98.90
Purchase #2	$79.69	13.479%	$90.4314	$90.43	$90.45	$90.40
Purchase #3	$185.46	7.311%	$199.019	$199.02	$199.00	$199.00
Purchase #4	$203.46	12.845%	$229.5944	$229.59	$229.60	$229.60
Purchase #5	$69.51	5.381%	$73.2503	$73.25	$73.25	$73.30
Purchase #6	$140.65	5.638%	$148.5798	$148.58	$148.60	$148.60
Purchase #7	$119.99	10.458%	$132.5386	$132.54	$132.55	$132.50
7 purchase totals =	$887.48		$972.2715	$972.27	$972.30	$972.30