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	$27.64	12.472%	$31.0873	$31.09	$31.10	$31.10
Purchase #2	$225.76	6.574%	$240.6015	$240.60	$240.60	$240.60
Purchase #3	$69.56	7.613%	$74.8556	$74.86	$74.85	$74.90
Purchase #4	$243.54	10.561%	$269.2603	$269.26	$269.25	$269.30
Purchase #5	$187.25	4.677%	$196.0077	$196.01	$196.00	$196.00
Purchase #6	$157.86	7.405%	$169.5495	$169.55	$169.55	$169.50
Purchase #7	$41.25	8.146%	$44.6102	$44.61	$44.60	$44.60
7 purchase totals =	$952.86		$1,025.9721	$1,025.98	$1,025.95	$1,026.00