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	$67.50	7.770%	$72.7448	$72.74	$72.75	$72.70
Purchase #2	$68.63	5.662%	$72.5158	$72.52	$72.50	$72.50
Purchase #3	$184.91	10.666%	$204.6325	$204.63	$204.65	$204.60
Purchase #4	$175.61	10.805%	$194.5847	$194.58	$194.60	$194.60
Purchase #5	$246.61	12.429%	$277.2612	$277.26	$277.25	$277.30
Purchase #6	$30.38	5.638%	$32.0928	$32.09	$32.10	$32.10
Purchase #7	$132.87	3.781%	$137.8938	$137.89	$137.90	$137.90
7 purchase totals =	$906.51		$991.7256	$991.71	$991.75	$991.70